Pages 309-398

Transcription

Pages 309-398

Incidental Catch of Halibut
309
IPHC REPORT OF ASSESSMENT AND RESEARCH ACTIVITIES 2007
310
Incidental catch and mortality of Pacific halibut, 1962-2007
Gregg H. Williams
Abstract
Estimates of the bycatch mortality of Pacific halibut (Hippoglossus stenolepis) in 2007 totaled
12.2 million pounds (net weight), a decrease of 5.6% from 2006 and the lowest seen since 1987.
Bycatch mortality decreased in most major regulatory areas from 2006. Most of the decrease is
attributable to lower bycatch in the Alaskan groundfish fishery. In Area 2A, bycatch mortality
decreased seven percent in 2006, despite an increase of trawl effort (hours). Bycatch mortality in
Area 2B remained slightly higher than in 2003-4. Lower trawl bycatch in Area 4 was the primary
reason for reduced bycatch mortality in that area.
Introduction
Fisheries targeting on other fish and shellfish inadvertently catch Pacific halibut (Hippoglossus
stenolepis). Information collected by at-sea observers has indicated the incidental catch, or bycatch,
is substantial. Regulations require that halibut be returned to the sea with no additional injury.
However, some fish do die from being caught and handled. The preliminary estimate of 2007
bycatch mortality is 12.2 million pounds. This is a decrease from 2006 and the lowest seen since
1987. This document provides an overview of areas and fisheries which contributed to halibut
bycatch mortality in 2007.
Sources of bycatch information and estimates
The International Pacific Halibut Commission (IPHC) relies upon information supplied by
observer programs for bycatch estimates in most fisheries. Research survey information is used
to generate estimates of bycatch in the few cases where fishery observations are unavailable.
The U.S. National Marine Fisheries Service (NMFS) operates observer programs covering the
groundfish fisheries off Alaska and the U.S. west coast, and provides IPHC with estimates of
bycatch. Estimates of bycatch off Alaska for 2007 were based on bycatch reported from fishing
conducted through mid-November and projections for the remainder of the year.
Estimates of bycatch mortality in crab pot and shrimp trawl fisheries off Alaska have been made
by IPHC staff from previous studies of these fisheries and are based on bycatch rates observed on
research surveys because direct fishery observations of bycatch are lacking.
The amount of information varies for fisheries conducted off British Columbia. For the trawl
fishery, bycatch is managed with an individual bycatch quota program instituted in 1996 by Canadian
Department of Fisheries and Oceans (DFO). Fishery observers sample the catch on each bottom
trawler, collecting data to estimate bycatch. Bycatch in other fisheries, such as the shrimp trawl,
sablefish pot, and rockfish hook-&-line fisheries, is largely unknown but is believed to be relatively
low, particularly for the shrimp trawl fishery (Boutillier et al. 1999). A new management program
in 2006 which included 100% at-sea monitoring (observers or video) required groundfish vessels
to account for their bycatch of all non-target species, and will likely provide new information on
halibut bycatch levels in many fisheries where little has been known.
311
Halibut bycatch in the domestic groundfish trawl fishery operating in Area 2A is estimated
from information collected by at-sea observers. Bycatch rates (number per hour) are derived from
the observer data, and applied to commercial fishery effort from logbooks (Wallace and Methot
2001). Most recent estimates have been provided by Wallace and Hastie (2007). Shrimp trawl
fishery bycatch estimates are provided by Oregon Department of Fish and Wildlife (ODFW) staff
from examinations of halibut bycatch during gear experiments. The estimates are considered rough
approximations given the limited amount of data available, but appear reasonable and are updated
every few years. Bycatch in the hook-&-line fishery has been determined through comparisons
with the Alaskan sablefish fishery (Williams et al. 1998).
Discard mortality rates and assumptions
Discard mortality rates (DMRs), used to determine the fraction of the estimated bycatch that
dies, vary by fishery and area. Where observers are used for fishery sampling, DMRs are calculated
from data collected on the release viability or injury of halibut. For areas without observers, assumed
DMRs are used, which are based on the similarity of fisheries to those in other areas where data
are available. The mortality models used to calculate these rates have been presented by Clark et
al. (1992) and Williams (1997).
Observer data are used to estimate DMRs in fisheries in two major areas. NMFS manages the
groundfish fisheries off Alaska according to a schedule of DMRs; the 2007 schedule is summarized
in Table 1. DMRs for previous years can be found in Williams (this volume). In Area 2B, observers
monitoring the Canadian trawl fishery examine each halibut to determine survival.
Data to determine DMRs for other fisheries are not available, so assumptions are made on likely
DMRs based on similar fisheries where DMRs are known. For Area 2A, the domestic groundfish
trawl and shrimp trawls are assumed to have a 50% mortality rate, whereas the unobserved hook-&line fishery for sablefish is assigned an assumed DMR of 25%. The midwater fishery for whiting is
assumed to have a 75% rate, based on the large catches of whiting typical of this type of fishery.
Bycatch mortality by regulatory area
Halibut bycatch mortality was relatively small until the 1960s, when it increased rapidly due
to the sudden development of the foreign trawl fisheries off the North American coast. The total
bycatch mortality (excluding the Japanese directed fishery in the eastern and western Bering Sea)
peaked in 1965 at about 21 million pounds (Fig. 1). Bycatch mortality declined during the late
1960s, but increased to about 20 million pounds in the early 1970s. During the late 1970s and
early 1980s, it dropped to roughly 13 million pounds, as foreign fishing off Alaska came under
increasing control. By 1985, bycatch mortality had declined to 7.2 million pounds, the lowest level
since the IPHC began its monitoring nearly 25 years earlier. Bycatch mortality increased in the
late 1980s, due to the growth of the U.S. groundfish fishery off Alaska, and peaked at 20.3 million
pounds in 1992. Bycatch mortality has since declined; preliminary estimates for 2007 total 12.2
million pounds, representing a 5.6% decrease from 2006 and a 40% decrease from the peak in
1992 of 20.3 million pounds. Bycatch mortality has ranged between 12-14 million pounds since
the late 1990s.
Estimates of bycatch mortality by fishery and major IPHC regulatory area for 1998 through
2007 are shown in Table 2 and discussed in the following sections. Tables 3 through 5 provide
312
bycatch mortality estimates by various area groupings. Tables 6 and 7 provide estimates of bycatch
mortality in the federally-managed Alaskan groundfish fisheries.
Area 2
Bycatch mortality in Area 2 in 2007 was estimated at 1.06 million pounds, up slightly from
2006 and below the 10-year average of 1.25 million pounds (Table 2). The primary sources for
bycatch mortality in Area 2 are the groundfish trawl fisheries in 2A and 2B, and the crab pot and
shrimp trawl fisheries in 2C.
NMFS estimated halibut bycatch mortality for the 2006 trawl fishery operating in Area 2A at
333,000 pounds, a 7% decrease from 2005 despite an increase of 8.2% increase in overall trawl
effort (Wallace and Hastie 2007). Trawl effort in depths less than 150 fm, where halibut bycatch
rates are generally higher, increased by only 2%. The 2006 estimate has been used for 2007, but
will be replaced when an actual estimate for 2007 is obtained. Finally, no new estimate of halibut
bycatch mortality is available for the shrimp trawl fishery, so the most recent estimate has been
rolled forward to 2007.
In Area 2B, trawl fishery bycatch mortality was estimated at 0.35 million pounds, an increase
of 18% from the 2005 estimate of 0.30 million pounds. This latest estimate is significantly above
the average of 0.26 million pounds which has occurred since 1996, when the Individual Bycatch
Quota program was started.
In Area 2C, crab pot fishing and shrimp trawling occur in various locations and harvests have
held steady over the years. Pot fishing for brown king crab (Lithodes aequispina) occurs in the
deep waters of Chatham Strait during the winter months, and beam trawling occurs for shrimp and
flounders in the inside waters of southeast Alaska. These fisheries have not been reviewed since
the early 1990s, but these fisheries are small scale in nature, with low bycatch. It is assumed that
mortality has been relatively stable since first examined.
Area 3
Bycatch mortality in Area 3 was estimated at 4.02 million pounds in 2007 (Table 2), an 8.2
percent decrease from 2006. The groundfish fishery continued to be affected by fishery closures
inside stellar sea lion critical habitat, which forced vessels to fish in less productive areas. In all
Gulf areas, the trawl fishery was more closely managed in 2007 to prevent overruns of fisheryspecific bycatch mortality limits. For some fisheries, NMFS required daily reporting by observers
to achieve this goal. Also, a study which permitted a portion of the rockfish trawl fishery to operate
as a fishery cooperative resulted in less than 82,000 pounds (50 t) of mortality for those vessels,
compared to 350,000-500,000 pounds (200-300 t) in previous years. Vessels participating in
the rockfish cooperative were able to fish more off-bottom and at a slower pace offered by the
cooperative structure. In other fisheries, the catch of Pacific cod, which typically accounts for
the majority of the halibut bycatch in Area 3 for all gear types, was similar to 2006. Pot effort for
cod, which has lower bycatch properties than other gears, continues to be quite high. Within Area
3B, trawl and hook-&-line fishery bycatch each dropped 13% from 2006. The total 2007 Area 3
bycatch mortality is below the 10-year average of 4.45 million pounds.
313
Area 4
Bycatch mortality in Area 4 was estimated at 7.1 million pounds, a drop of 5.5% from 2006.
Since 1998, bycatch mortality in this area has ranged from 6.8 to 7.7 million pounds annually,
averaging 7.3 million pounds. This year’s estimate is slightly below the long term average.
For 2007, an 11% decrease in trawl fishery bycatch was somewhat offset by minor increases
in bycatch by the hook & line and Community Development Quota (CDQ) fisheries. Driven by
cod fishing, bycatch by hook & line gear increased markedly, even with lower cod quotas. CDQ
fisheries also expanded their effort on cod, which previously they had fished primarily on pollock.
Within the non-CDQ trawl fisheries, big decreases in bycatch by the cod and arrowtooth flounder
fisheries were offset by bycatch increases in the midwater pollock, rock sole, and Atka mackerel
fisheries.
References
Boutillier, J. A., Bond, J. A. and Nguyen, H. 1999. Halibut by-catch in the British Columbia shrimp
trawl fishery. Canadian Stock Assessment Secretariat Research Doc. No. 99/122.
Clark, W. G., Hoag, S. H., Trumble, R. J., and Williams, G. H. 1992. Re-estimation of survival for
trawl caught halibut released in different condition factors. Int. Pac. Halibut Comm. Report of
Assessment and Research Activities 1992: 197-206.
Wallace, J. and Methot, R. 2001. Estimates of Pacific halibut bycatch and mortality in IPHC Area
2A in 2000. NOAA, Northwest Fisheries Science Center. Report submitted to the Pacific
Fishery Management Council’s Scientific and Statistical Committee, September, 2001.
Wallace, J. and Hastie, J. 2007. Pacific halibut bycatch in IPHC Area 2A in the 2006 groundfish
trawl fishery. NOAA, Northwest Fisheries Science Center. Report submitted to the Pacific
Fishery Management Council’s Scientific and Statistical Committee, September, 2007. 12 p.
Williams, G. H. 1997. Pacific halibut discard mortality rates in the 1990-1995 Alaskan groundfish
fisheries, with recommendations for monitoring in 1997. Int. Pac. Halibut Comm. Report of
Assessment and Research Activities 1996: 211-227.
Williams, G. H. 2007. Pacific halibut discard mortality rates in the 2005 groundfish fisheries, and
recommendations for discard mortality rates for monitoring halibut bycatch in 2007-2009. Int.
Pac. Halibut Comm. Report of Assessment and Research Activities 2006:175-188.
Williams, G., Stauffer, G., Weeks, H., Saelens, M., Scordino, J., Bodenmiller, D., and Northup,
T. 1998. Pacific halibut bycatch in Area 2A: Bycatch rates and current estimates of bycatch
mortality. Int. Pac. Halibut Comm. Report of Assessment and Research Activities 1997: 269282.
314
Table 1. Preseason assumed discard mortality rates used by NMFS for monitoring halibut
bycatch mortality in 2007-2009 in the Alaskan groundfish fisheries. From Williams (2007)
and Williams (this volume).
Bering Sea/Aleutians
Recommendation
Gear/Target
for 2007-2009
Trawl
Atka mackerel
76
Bottom pollock
74
Pacific cod
70
Other Flatfish
74
Rockfish
76
Flathead sole
70
Pelagic pollock
88
Rock sole
80
Sablefish
75
Turbot
70
Arrowtooth fldr
75
Yellowfin sole
80
Pot
Pacific cod
7
Longline
Pacific cod
11
Rockfish
17
Turbot
13
Gulf of Alaska
Recommendation
for 2007-2009
Gear/Target
Trawl
Atka mackerel
Bottom pollock
Pacific cod
Deepwater flatfish
Shallow water flatfish
Rockfish
Flathead sole
Pelagic pollock
Sablefish
Arrowtooth fldr
Rex sole
Pot
Pacific cod
Longline
Pacific cod
Rockfish
60
59
63
53
71
67
61
76
65
69
63
16
14
10
CDQ Fisheries
Recommended
Gear/Target
DMR for 2008
Trawl
Atka mackerel
85
Bottom pollock
86
Rockfish
82
Flathead sole
87
Pelagic pollock
90
Rock sole
86
Yellowfin sole
86
Pot
Sablefish
34
Longline
Pacific cod
10
Turbot
4
315
Table 2. Estimates (thousands of pounds, net weight) of bycatch mortality of Pacific halibut
(Hippoglossus stenolepis) by year, area, and fishery for 1996 through 2007. Estimates for 2007 are
preliminary and subject to change as new information becomes available.
Region and Area
AREA 2A
Groundfish Trawl
Shrimp Trawl
Hook & Line
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
Total
1,041
25
16
1,082
946
25
16
987
781
25
16
822
796
25
16
837
512
25
16
553
462
25
16
503
245
25
16
286
358
25
16
399
333
25
16
374
333
25
16
374
Total
213
213
193
193
230
230
177
177
244
244
244
244
251
251
346
346
294
294
348
348
AREA 2C
Crab Pot/Shrimp Trawl
Groundfish Trawl
Hook & Line (non-IFQ)
Hook & Line (IFQ)
Chatham Str. Sablefish
Clarence Str. Sablefish
Total
AREA 2 Subtotal
303
4
18
3
8
25
361
1,656
303
1
18
3
8
25
358
1,538
303
0
56
3
8
25
395
1,447
303
0
2
3
8
25
341
1,355
303
0
1
3
8
25
340
1,137
303
0
2
3
8
25
341
1,088
303
0
23
3
8
25
362
899
303
0
1
3
8
25
340
1,085
303
0
2
3
8
25
341
1,009
303
0
3
3
8
25
342
1,064
250
1,908
360
119
15
10
2,662
250
2,148
317
119
41
10
2,885
250
2,222
281
119
10
10
2,892
250
2,404
203
119
23
10
3,009
250
1,685
128
119
2
10
2,194
250
2,407
389
119
5
10
3,180
250
3,033
244
119
15
10
3,671
250
2,664
149
119
28
10
3,220
250
2,339
239
119
18
10
2,975
250
2,218
167
119
7
10
2,771
50
1,130
89
116
4
1,389
4,051
50
1,184
281
116
106
1,737
4,622
50
1,194
143
116
7
1,510
4,402
50
1,320
171
116
18
1,675
4,684
50
1,508
248
116
2
1,924
4,118
50
1,341
198
116
29
1,734
4,914
50
866
205
116
37
1,274
4,945
50
862
69
116
29
1,126
4,346
50
926
299
116
9
1,400
4,375
50
806
260
116
12
1,244
4,015
300
5,795
1,409
60
11
150
7,725
300
5,972
982
60
11
187
172
7,684
300
5,379
1,508
60
24
64
106
7,441
300
5,322
1,300
60
13
57
68
7,120
300
5,591
1,058
60
17
131
116
7,273
300
5,589
556
60
28
187
102
6,822
300
5,499
617
60
6
176
77
6,735
300
6,454
666
60
2
128
82
7,692
300
6,269
593
60
8
187
74
7,491
300
5,590
797
60
2
247
85
7,081
13,432
13,844
13,290
13,159
12,528
12,824
12,579
13,123
12,875
12,160
AREA 2B
Domestic Trawl
AREA 3A
Groundfish Trawl
Hook & Line (IFQ)
Groundfish Pot
Pr Wm Sd Sablefish
Total
AREA 3B
Groundfish Trawl
Hook & Line (IFQ)
Groundfish Pot
Total
AREA 3 Subtotal
AREA 4
Groundfish Trawl
Hook & Line (IFQ)
Groundfish Pot
CDQ Trawl
CDQ Hook & Line
AREA 4 Subtotal
GRAND TOTAL
316
Table 3. Estimates (thousands of pounds, net weight and metric tons, round weight) of bycatch
mortality of Pacific halibut (Hippoglossus stenolepis) from all sources by IPHC regulatory area
for 1962 through 2006. Estimates for 2006 are preliminary and subject to change as new
information becomes available.
Year
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
Thousands of Pounds, net weight
Area 2
Area 3
Area 4
Total
1,383
1,283
1,310
1,640
1,879
2,091
2,478
2,651
2,032
2,284
2,506
2,357
2,738
3,025
3,249
2,874
2,325
3,149
2,368
2,169
1,644
1,723
1,851
1,915
1,940
2,428
2,389
2,278
2,943
3,133
2,925
2,847
2,191
2,484
1,258
1,226
1,656
1,538
1,447
1,355
1,137
1,088
899
1,085
1,009
1,064
3,083
6,102
11,639
16,539
12,495
9,528
7,053
4,980
6,230
4,341
7,099
7,147
8,667
5,231
5,938
5,988
4,895
6,715
7,099
6,282
5,972
4,892
3,647
1,578
1,246
3,113
3,415
4,085
6,159
6,514
6,650
5,353
5,294
4,723
4,700
4,408
4,051
4,622
4,402
4,684
4,118
4,914
4,945
4,346
4,375
4,015
4,143
2,038
2,965
3,182
3,400
4,718
5,685
7,599
8,028
13,095
9,675
8,029
7,620
3,650
4,564
2,914
5,023
5,419
9,235
6,408
4,756
4,269
4,692
4,207
5,576
5,738
8,858
7,282
8,580
10,022
10,718
7,764
9,466
8,726
8,507
7,880
7,725
7,684
7,441
7,120
7,273
6,822
6,735
7,692
7,491
7,081
8,609
9,423
15,914
21,361
17,774
16,337
15,216
15,230
16,290
19,720
19,280
17,533
19,025
11,906
13,751
11,776
12,242
15,282
18,702
14,859
12,373
10,883
10,189
7,700
8,762
11,279
14,662
13,646
17,682
19,669
20,293
15,964
16,951
15,933
14,465
13,514
13,432
13,844
13,290
13,159
12,528
12,824
12,579
13,123
12,875
12,160
Area 2
834
774
790
989
1,133
1,261
1,495
1,599
1,225
1,377
1,512
1,422
1,651
1,825
1,960
1,733
1,402
1,899
1,428
1,308
992
1,039
1,116
1,155
1,170
1,465
1,441
1,374
1,775
1,890
1,764
1,717
1,322
1,498
759
739
999
928
873
817
686
656
542
654
609
642
Metric tons, round weight
Area 3
Area 4
1,860
3,681
7,020
9,976
7,537
5,747
4,254
3,004
3,758
2,618
4,282
4,311
5,228
3,155
3,582
3,612
2,952
4,050
4,282
3,789
3,602
2,951
2,199
952
752
1,878
2,060
2,464
3,715
3,929
4,011
3,229
3,193
2,849
2,835
2,659
2,443
2,788
2,655
2,825
2,484
2,964
2,983
2,621
2,639
2,422
2,499
1,229
1,788
1,919
2,051
2,846
3,429
4,584
4,842
7,899
5,836
4,843
4,596
2,202
2,753
1,758
3,029
3,269
5,570
3,865
2,869
2,575
2,830
2,538
3,363
3,461
5,343
4,393
5,175
6,045
6,465
4,683
5,710
5,263
5,131
4,753
4,660
4,635
4,488
4,295
4,387
4,115
4,062
4,640
4,518
4,271
Total
5,192
5,683
9,599
12,884
10,721
9,854
9,178
9,186
9,825
11,894
11,629
10,575
11,475
7,181
8,294
7,103
7,384
9,218
11,280
8,963
7,463
6,564
6,146
4,644
5,285
6,803
8,844
8,231
10,665
11,864
12,240
9,629
10,224
9,610
8,725
8,151
8,102
8,350
8,016
7,937
7,556
7,735
7,587
7,915
7,766
7,335
317
Table 4. Estimates (thousands of pounds, net weight and metric tons, round weight) of bycatch mortality
of Pacific halibut (Hippoglossus stenolepis) from all sources by IPHC regulatory subarea for 1962 through
2007. Estimates for 2007 are preliminary and subject to change as new information becomes available.
Thousands of pounds, net weight
Year
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
Area
2A
477
477
477
477
477
476
476
475
475
476
475
475
476
476
477
477
408
408
444
444
444
614
614
614
1,082
987
822
837
553
503
286
399
374
374
Area
2B
1,176
1,077
1,105
1,435
1,666
1,652
1,963
2,183
1,470
1,745
1,750
1,509
1,729
1,909
2,064
1,817
1,471
1,852
1,372
1,188
867
943
1,074
1,139
1,161
1,649
1,609
1,498
1,679
1,992
1,745
1,661
1,219
1,522
299
215
213
193
230
177
244
244
251
346
294
348
Area
2C
207
206
205
205
213
439
515
468
562
539
756
848
532
639
708
580
377
821
520
507
302
304
302
301
303
303
303
303
856
733
736
742
528
348
345
397
361
358
395
341
340
341
362
340
341
342
Area
3A
1,919
3,314
9,370
6,097
4,513
4,633
5,476
3,806
3,389
2,974
5,406
4,452
5,247
3,158
3,495
4,094
3,055
5,780
5,852
4,720
3,797
2,957
2,140
1,001
836
2,240
3,365
3,267
4,114
4,843
4,668
4,291
3,907
2,963
2,743
2,965
2,662
2,885
2,892
3,009
2,194
3,180
3,671
3,220
2,975
2,771
Area
3B
1,164
2,788
2,269
10,442
7,982
4,895
1,577
1,174
2,841
1,367
1,693
2,695
3,420
2,073
2,443
1,894
1,840
935
1,246
1,563
2,175
1,935
1,507
577
410
873
50
818
2,045
1,671
1,982
1,062
1,387
1,760
1,957
1,443
1,389
1,737
1,510
1,675
1,924
1,734
1,274
1,126
1,400
1,244
Area
4
4,143
2,038
2,965
3,182
3,400
4,718
5,685
7,599
8,028
13,095
9,675
8,029
7,620
3,650
4,564
2,914
5,023
5,419
9,235
6,408
4,756
4,269
4,692
4,207
5,576
5,738
8,858
7,282
8,580
10,022
10,718
7,764
9,466
8,726
8,507
7,880
7,725
7,684
7,441
7,120
7,273
6,822
6,735
7,692
7,491
7,081
Total
8,609
9,423
15,914
21,361
17,774
16,337
15,216
15,230
16,290
19,720
19,280
17,533
19,025
11,906
13,751
11,776
12,242
15,282
18,702
14,859
12,373
10,883
10,189
7,700
8,762
11,279
14,662
13,646
17,682
19,669
20,293
15,964
16,951
15,933
14,465
13,514
13,432
13,844
13,290
13,159
12,528
12,824
12,579
13,123
12,875
12,160
318
Area
2A
288
288
288
288
288
287
287
287
287
287
287
287
287
287
288
288
246
246
268
268
268
370
370
370
653
595
496
505
334
303
173
241
226
226
Area
2B
709
649
667
866
1,005
996
1,184
1,317
886
1,052
1,056
910
1,043
1,151
1,245
1,096
887
1,117
828
716
523
568
648
687
700
995
971
904
1,013
1,202
1,053
1,002
735
918
180
130
128
116
139
107
147
147
151
209
177
210
Area
Area
Area
2C
3A
3B
125
1,157
702
124
1,999
1,682
124
5,652
1,369
124
3,678
6,298
128
2,722
4,815
265
2,795
2,953
311
3,303
951
282
2,296
708
339
2,044
1,714
325
1,794
825
456
3,261
1,021
511
2,685
1,626
321
3,165
2,063
385
1,905
1,250
427
2,108
1,474
350
2,469
1,142
227
1,843
1,110
495
3,486
564
314
3,530
752
306
2,847
942
182
2,290
1,312
183
1,784
1,167
182
1,290
909
182
604
348
183
504
247
183
1,351
527
183
2,030
30
183
1,971
494
516
2,481
1,233
442
2,921
1,008
444
2,816
1,195
448
2,588
641
318
2,357
837
210
1,787
1,062
208
1,655
1,180
239
1,788
870
218
1,606
838
216
1,740
1,048
238
1,744
911
206
1,815
1,010
205
1,323
1,161
206
1,918
1,046
218
2,214
768
205
1,942
679
206
1,794
844
206
1,671
750
Area
4
2,499
1,229
1,788
1,919
2,051
2,846
3,429
4,584
4,842
7,899
5,836
4,843
4,596
2,202
2,753
1,758
3,029
3,269
5,570
3,865
2,869
2,575
2,830
2,538
3,363
3,461
5,343
4,393
5,175
6,045
6,465
4,683
5,710
5,263
5,131
4,753
4,660
4,635
4,488
4,295
4,387
4,115
4,062
4,640
4,518
4,271
Total
5,192
5,683
9,599
12,884
10,721
9,854
9,178
9,186
9,825
11,894
11,629
10,575
11,475
7,181
8,294
7,103
7,384
9,218
11,280
8,963
7,463
6,564
6,146
4,644
5,285
6,803
8,844
8,231
10,665
11,864
12,240
9,629
10,224
9,610
8,725
8,151
8,102
8,350
8,016
7,937
7,556
7,735
7,587
7,915
7,766
7,335
Table 5. Estimates (thousands of pounds, net weight and metric tons, round weight) of bycatch
mortality of Pacific halibut (Hippoglossus stenolepis) from all sources by geographic region of the
coast for 1962 through 2007. Estimates for 2007 are preliminary and subject to change as new
information becomes available.
Year
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
Thousands of Pounds, net weight
Bering
Wash.,Oreg.,
Gulf of
Sea &
Calif.
B.C.
Alaska
Aleut.
1,176
3,290
4,143
1,077
6,308
2,038
1,105
11,844
2,965
1,435
16,744
3,182
1,666
12,708
3,400
1,652
9,967
4,718
1,963
7,568
5,685
2,183
5,448
7,599
1,470
6,792
8,028
1,745
4,880
13,095
1,750
7,855
9,675
1,509
7,995
8,029
477
1,729
9,199
7,620
477
1,909
5,870
3,650
477
2,064
6,646
4,564
477
1,817
6,568
2,914
477
1,471
5,272
5,023
476
1,852
7,536
5,419
476
1,372
7,619
9,235
475
1,188
6,789
6,408
475
867
6,274
4,756
476
943
5,196
4,269
475
1,074
3,949
4,692
475
1,139
1,879
4,207
476
1,161
1,549
5,576
476
1,649
3,416
5,738
477
1,609
3,718
8,858
477
1,498
4,388
7,282
408
1,679
7,015
8,580
408
1,992
7,247
10,022
444
1,745
7,386
10,718
444
1,661
6,095
7,764
444
1,219
5,822
9,466
614
1,522
5,071
8,726
614
299
5,045
8,507
614
215
4,805
7,880
1,082
213
4,412
7,725
987
193
4,980
7,684
822
230
4,797
7,441
837
177
5,025
7,120
553
244
4,458
7,273
503
244
5,255
6,822
286
251
5,307
6,735
399
346
4,686
7,692
374
294
4,716
7,491
374
348
4,357
7,081
Total
8,609
9,423
15,914
21,361
17,774
16,337
15,216
15,230
16,290
19,720
19,280
17,533
19,025
11,906
13,751
11,776
12,242
15,282
18,702
14,859
12,373
10,883
10,189
7,700
8,762
11,279
14,662
13,646
17,682
19,669
20,293
15,964
16,951
15,933
14,465
13,514
13,432
13,844
13,290
13,159
12,528
12,824
12,579
13,123
12,875
12,160
Wash.,Oreg.,
Calif.
288
288
288
288
288
287
287
287
287
287
287
287
287
287
288
288
246
246
268
268
268
370
370
370
653
595
496
505
334
303
173
241
226
226
Bering
Gulf of
Sea &
B.C.
Alaska
Aleut.
709
1,984
2,499
649
3,805
1,229
667
7,144
1,788
866
10,100
1,919
1,005
7,665
2,051
996
6,012
2,846
1,184
4,565
3,429
1,317
3,286
4,584
886
4,097
4,842
1,052
2,943
7,899
1,056
4,738
5,836
910
4,822
4,843
1,043
5,549
4,596
1,151
3,541
2,202
1,245
4,009
2,753
1,096
3,962
1,758
887
3,180
3,029
1,117
4,545
3,269
828
4,595
5,570
716
4,095
3,865
523
3,784
2,869
568
3,134
2,575
648
2,382
2,830
687
1,133
2,538
700
934
3,363
995
2,060
3,461
971
2,243
5,343
904
2,647
4,393
1,013
4,231
5,175
1,202
4,371
6,045
1,053
4,455
6,465
1,002
3,676
4,683
735
3,512
5,710
918
3,059
5,263
180
3,043
5,131
130
2,898
4,753
128
2,661
4,660
116
3,004
4,635
139
2,893
4,488
107
3,031
4,295
147
2,689
4,387
147
3,170
4,115
151
3,201
4,062
209
2,826
4,640
177
2,845
4,518
210
2,628
4,271
Total
5,192
5,683
9,599
12,884
10,721
9,854
9,178
9,186
9,825
11,894
11,629
10,575
11,475
7,181
8,294
7,103
7,384
9,218
11,280
8,963
7,463
6,564
6,146
4,644
5,285
6,803
8,844
8,231
10,665
11,864
12,240
9,629
10,224
9,610
8,725
8,151
8,102
8,350
8,016
7,937
7,556
7,735
7,587
7,915
7,766
7,335
319
Table 6. Estimates (thousands of pounds, net weight and metric tons, round weight) of the bycatch
mortality of Pacific halibut (Hippoglossus stenolepis) from the Alaskan groundfish fishery for 1990
through 2007. Estimates for 2007 are preliminary and subject to change as new information
becomes available. All federally managed fisheries are represented, including the IFQ sablefish
fishery and Community Development Quota (CDQ) fisheries. However, fisheries operating
within State of Alaska jurisdiction, e.g., Chatham Strait sablefish fishery, are excluded.
Year
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
Gulf of Alaska
Trawls
H&L
Pot
Total
Trawls
H&L
Pot
4,331
2,012
52
6,395
2,612
1,214
31
4,538
2,081
7
6,626
2,737
1,255
4
4,060
2,684
26
6,770
2,449
1,619
16
3,548
1,900
19
5,467
2,140
1,146
19
3,619
1,512
23
5,154
2,183
912
14
3,745
645
35
4,425
2,259
389
21
3,890
498
11
4,399
2,346
300
7
3,291
855
13
4,159
1,985
516
8
3,042
705
19
3,766
1,835
425
11
3,333
854
147
4,334
2,010
515
89
3,416
718
17
4,151
2,060
433
10
3,724
614
41
4,379
2,246
370
25
3,193
615
4
3,812
1,926
371
2
3,748
827
34
4,609
2,261
499
21
3,899
710
52
4,661
2,352
428
31
3,526
457
57
4,040
2,127
276
34
3,265
778
27
4,070
1,969
469
16
3,024
668
19
3,711
1,824
403
11
Year
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
Trawls
H&L
Pot
Total
Trawls
H&L
Pot
4,331
2,012
52
6,395
2,612
1,214
31
4,538
2,081
7
6,626
2,737
1,255
4
4,060
2,684
26
6,770
2,449
1,619
16
3,548
1,900
19
5,467
2,140
1,146
19
3,619
1,512
23
5,154
2,183
912
14
3,745
645
35
4,425
2,259
389
21
3,890
498
11
4,399
2,346
300
7
3,291
855
13
4,159
1,985
516
8
3,042
705
19
3,766
1,835
425
11
3,333
854
147
4,334
2,010
515
89
3,416
718
17
4,151
2,060
433
10
3,724
614
41
4,379
2,246
370
25
3,193
615
4
3,812
1,926
371
2
3,748
827
34
4,609
2,261
499
21
3,899
710
52
4,661
2,352
428
31
3,526
457
57
4,040
2,127
276
34
3,265
778
27
4,070
1,969
469
16
3,024
668
19
3,711
1,824
403
11
320
Total
3,857
3,997
4,083
3,305
3,109
2,669
2,653
2,509
2,272
2,614
2,504
2,641
2,299
2,780
2,811
2,437
2,455
2,238
Total
3,857
3,997
4,083
3,305
3,109
2,669
2,653
2,509
2,272
2,614
2,504
2,641
2,299
2,780
2,811
2,437
2,455
2,238
Table 6. (Continued)
Year
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
Alaska Total
Trawls
H&L
Pot
Total
Trawls
H&L
Pot
Total
10,640
2,639
56
13,335
6,418
1,592
34
8,043
12,792
3,545
11
16,348
7,716
2,138
7
9,861
11,682
5,459
47
17,188
7,046
3,293
28
10,367
10,151
2,761
19
12,931
6,123
1,665
19
7,807
10,818
3,456
32
14,306
6,525
2,085
19
8,629
10,355
2,376
60
12,791
6,246
1,433
36
7,715
10,472
2,033
41
12,546
6,316
1,226
25
7,567
9,238
2,419
22
11,679
5,572
1,459
13
7,044
8,987
2,114
30
11,131
5,421
1,275
18
6,714
9,492
2,068
158
11,718
5,725
1,247
95
7,068
8,859
2,392
41
11,292
5,344
1,443
25
6,811
9,103
2,042
54
11,199
5,491
1,232
33
6,755
8,915
1,849
21
10,785
5,377
1,115
13
6,505
9,524
1,545
62
11,131
5,745
932
37
6,714
9,574
1,464
58
11,096
5,775
883
35
6,693
10,108
1,265
59
11,432
6,097
763
36
6,895
9,721
1,505
35
11,261
5,863
908
21
6,792
8,861
1,610
21
10,492
5,345
971
13
6,329
321
Table 7. Estimates of 2007 groundfish catch and Pacific halibut bycatch mortality by region,
gear and target fishery in the groundfish fisheries off Alaska. Does not include IFQ or CDQ
fisheries. Data current through October 27, 2007.
Region & Target
fishery
Bering Sea
Alaska plaice
Arrowtooth flndr
Atka mackerel
Bottom pollock
Flathead sole
Midwater pollock
Other flatfish
Other species
Pacific cod
Rock sole
Rockfish
Sablefish
Turbot
Yellowfin sole
Total
Gulf of Alaska
Arrowtooth flndr
Bottom pollock
Deepwater flats
Flathead sole
Midwater pollock
Pacific cod
Rex sole
Rockfish
Sablefish
Shallow water flats
Total
Pot
Hook & Line
Groundfish
Catch (mt)
Hbt Byc
Mort (mt)
Groundfish
Catch (mt)
Trawl
Hbt Byc
Mort (mt)
110
1
50
83,873
0
475
11
0
1,515
5
85,560
481
2
0
11,542
259
22,642
11
11,544
259
22,642
11
322
16,031
0
754
1
16,785
1
Groundfish
Catch (mt)
Hbt Byc
Mort (mt)
195
1,212
58,112
25,918
20,971
968,134
3,057
269
91,369
36,982
12,117
1
17
222
30
305
238
60
4
1,042
910
23
120,357
1,338,692
518
3,372
20,056
13,157
22
1,591
15,526
14,046
5,927
18,726
388
12,564
102,003
435
88
0
17
1
467
132
99
5
581
1,824
Bycatch Mortality (million lbs
25
Area 4
Area 3
Area 2
20
15
10
5
0
1962
1967
1972
1977
1982
1987
1992
1997
2002
2007
Year
Figure 1. Bycatch mortality of Pacific halibut by IPHC regulatory area, 1962-2007.
323
324
Pacific halibut discard mortality rates in the 2006 open
access and CDQ groundfish fisheries, and recommendations
for discard mortality rates needed for monitoring halibut
bycatch in 2008 CDQ fisheries
Gregg H. Williams
Abstract
Observations of the physical condition and injuries of halibut caught as bycatch in the
groundfish fisheries off Alaska were used to determine discard mortality rates (DMRs). DMRs
were calculated for each target fishery (open access, and Community Development Quota or CDQ)
in the Gulf of Alaska and the Bering Sea/Aleutians regions. The resultant 2006 fishery DMRs
differed very little from 2005. Bycatch management for 2007-2009 is to be based on the DMRs
adopted by the North Pacific Fishery Management Council in September, 2006. Recommendations
for CDQ fisheries in 2008 were based on mean DMRs calculated from 1998-2006 data.
Introduction
Pacific halibut discard mortality rates (DMRs) in the Alaskan groundfish fisheries are estimated
from viability (injury and condition) data collected by National Marine Fisheries Service (NMFS)
observers. Analysis by staff of the International Pacific Halibut Commission (IPHC) results in
recommendations to the North Pacific Fishery Management Council (NPFMC or Council) for
managing halibut bycatch in subsequent fishing seasons. This paper describes the results from an
analysis of data collected from the 2006 open access and Community Development Quota (CDQ)
groundfish fisheries, and includes DMR recommendations for monitoring halibut bycatch in the
2008 CDQ fisheries.
Data description and methods
The analysis followed the same approach that has been employed since 1996, which was
described by Williams (1996). Observer haul data from the NMFS groundfish observer database
formed the basis of the analysis. The data records included the catch of groundfish by species or
species group, estimates of the number and weight (kg) of halibut bycatch, and the number and
length of halibut sampled for release condition or injury by category (excellent/poor/dead for trawl
and pot gear, minor/moderate/severe/dead for longline gear). Records for all hauls sampled by
observers in 2006 were obtained; hauls not sampled for species composition were excluded.
The records were assigned to target fishery categories, based on the catch of the particular
species within the haul catch composition, relative to the overall total and retained catches (Table
1). For example, hauls were coded as midwater pollock if pollock comprised 95% or more of the
summed total catch for the week (Sunday-Saturday). The determination for the flatfish targets
assumed that all arrowtooth flounder caught in a haul were discarded; the remaining species were
assumed to be retained. Target determination was based on the species/species group comprising
the greatest percentage of the “retained” catch. Flatfish targets in the Bering Sea/Aleutians (BSA)
325
were determined in a succession of comparisons of individual flatfish species compositions in the
catch. Table 1 shows the target codes and definitions used.
NMFS observers examined halibut for their release condition or injury immediately before
being returned to the sea. Each fish was judged according to a set of criteria (Williams and Chen
2003), which were used to determine internal and external injuries, and body damage from predators
(e.g., amphipods and marine mammals). Beginning in 2000, a dichotomous key was introduced to
reduce subjectivity in the determinations of condition and injury. Observers recorded the number
of halibut in excellent, poor and dead condition (trawls and pots) or with minor, moderate, severe
injuries, or deemed dead (longlines) each haul or set sampled, respectively. Samples were only
collected on hauls that were sampled for species composition. The species composition sampling
provides an estimate of the total number of halibut caught in the haul, as well as the catch of
groundfish, necessary for determining the target. Observers were instructed to limit the number
of fish examined to a maximum of 20, although this was occasionally exceeded by enthusiastic
observers.
Next, the viability distribution was calculated. First, for each haul, the proportion of halibut
in each category was extrapolated upwards to the total number of halibut caught. The extrapolated
numbers of halibut for each vessel by viability category were then summed within each region/
gear/target strata.
The general model for calculating the DMR for halibut caught by gear g was of the form:
4
d
DMRg = ¦ mi , g u Pi
i 1
i
where m is the mortality rate for gear g, and P is the proportion of halibut in condition i, where 1 is
excellent/minor, 2 is poor/moderate, 3 is dead (trawl or pot)/severe, and 4 is dead (longline).
The mortality rate m varies among gear types (see Clark et al. (1992) for trawls, Williams
(1996) for pots, and Kaimmer and Trumble (1998) for longlines) and represents the aggregate
effects of external and internal injuries to the fish and the presence of predation by amphipods or
marine mammals. There can be many sources of injuries, which vary by gear type. For longlines,
injuries are most frequently caused by improper release methods used by vessel crews. Another
significant factor is the length of the soak time, which can exacerbate the mortality caused by
hooking injuries and also increase the potential for amphipod predation. Estimated halibut mortality
rates by gear and condition/injury were as follows:
Gear (g)
Trawl
Pot
Longlines
mexc
0.20
0.00
mminor
0.035
mpoor
0.55
1.00
mmoderate
0.363
mdead
0.90
1.00
msevere
0.662
mdead
1.00
Mean fishery DMRs and associated standard errors were estimated by assuming that each
vessel acts as a separate sampling unit, so that a DMR was calculated for each individual vessel
in a target fishery. The DMR for a target fishery was then estimated as the mean of vessel DMRs,
326
where the vessel’s proportion of the total number of bycaught halibut was used as a weighting
factor, as follows:
Let DMRv = observed DMR on vessel v
= proportion of total number of halibut caught on vessel v in a fishery
pv
¦bp
n
DMR =
Then
v
u DMRv
v 1
g
Standard errors of the weighted mean DMR were estimated as:
d
V DMR
i
¦cp
n
v 1
2
v
b
u V DMRv
gh
d i V d DMRi
where V b DMR g is the sample variance of all the DMRs
and
SE DMR
v
v
d
i
d
i
, and V DMR and SE DMR are the
variance and standard error of DMR , respectively.
Results
Open access fisheries
A summary of observer coverage, sampling, and halibut size composition data is shown in
Table 2. Coverage and sampling in the major targets produced a large number of sampled hauls,
and a substantial number of halibut sampled. For example, observers sampled slightly more than
13,000 hauls and 16,000 halibut in the BSA midwater pollock fishery, which represents the largest
sample of any target fishery in 2006. Sample sizes were also very high (>1,000 hauls and/or >900
halibut measured) in the BSA cod (trawl), bottom pollock, rock sole, yellowfin sole and Atka
mackerel fisheries. More intermediate in sample size was flathead sole. Sampling in the remaining
BSA trawl fisheries was relatively low. The longline fishery for cod was the only BSA longline
fishery to receive much sampling; only minimal sampling occurred on vessels targeting rockfish
and turbot. Pot fishing was focused on cod, as in past years.
Most of the sampling in GOA trawl fisheries occurred in the pollock, cod, rockfish, and flatfish
targets, which continued patterns seen in past years. In 2006, the rockfish fishery contained the
greatest number of vessels (36) and hauls (554) monitored. Sampling of the cod and the two pollock
fisheries occurred at similar levels (33-34 vessels; ~200-400 hauls). Sampling of flatfish fishing
was concentrated in the shallow water, flathead and rex sole targets. For the second year in a row,
no vessel effort was noted in the deepwater flatfish target, which primarily has been directed at
Dover sole. In 2005, high catches of Dover sole were most frequently associated with even greater
catches of arrowtooth flounder or rex sole, and to a lesser extent flathead sole. Consequently,
vessel effort was assigned to those targets and not to deepwater flatfish. The number of sampled
longline and pot vessels targeting cod was similar to past years.
Data on sampling levels and release viability (condition or injury) by fishery and region are
summarized in Table 3. The raw data represent the observations recorded by observers. In most
cases, these raw data total less than those shown in Table 2, as the latter include halibut which were
327
not examined for condition/injury. The observations on each haul were extrapolated upwards to the
total number of halibut caught on the haul, and then summed across vessel & target fishery strata.
For most fisheries, the distribution of the extrapolated viability data is very similar to the raw
data. However, for the GOA bottom pollock fishery, the final, extrapolated data exhibit a different
distribution than the raw data. The complete time series of fishery DMRs is provided in Tables 4
and 5 for the BSA and GOA, respectively.
CDQ fisheries
In 2006, CDQ fishing was conducted using pots, trawls, and longlines. Species targeted by
trawl included pollock, rockfish, Atka mackerel, rock sole and yellowfin sole. Pacific cod were
targeted by longline, and sablefish by pots. Sampling levels and injury/viability data for CDQ
operations are summarized in Table 6; the time series of mean annual DMRs is shown in Table 7.
Almost all halibut caught in the trawl operations were dead when examined. The resulting
DMRs ranged from 0.88 to 0.90, which are generally higher than what is seen in open access
fishing for the same target species, with the exception of pelagic pollock and yellowfin sole.
Longline CDQ fishing consisted of 20 vessels targeting cod. Distribution of release injuries to
halibut in the CDQ longline cod fishery was similar to that observed in the open access cod fishery,
which is reflected by very similar DMRs (0.104 vs. 0.098).
Pot effort in 2006 was focused on sablefish, with four vessels observed, compared to five
vessels observed in 2005. The fishery DMR (0.404) was slightly higher than the long term mean and
what has been previously seen in this fishery. Pot soak time is believed to be positively correlated
with halibut mortality. The long soaks increase the potential for amphipod predation and injury
from hard-shell crab in the pot.
Recommendations for 2008
CDQ fisheries
Until 10 years of data from CDQ fishing have been collected, recommendations will be based
on averaging all available data. Thus, for the 2008 recommendations, a mean annual DMR for all
targets was calculated using data from 1998-2006. For the major species, there are at least five
years of data, and up to eight years for pelagic pollock and longline cod. These recommendations
are shown in Table 8.
For those targets with no recent information, such as trawl flathead sole and rockfish, longline
turbot, and pot cod, DMRs derived from open access fisheries data are recommended. The current
open access fisheries are probably more alike the current CDQ fishing, than data from fishing
conducted over five years ago or more.
Note on open access fisheries
The Council is using a plan in which the DMRs used to monitor halibut bycatch are an average
of data from the preceding 10 year period. These 10-year mean DMRs for each fishery are used
for a 3-year period, with the justification being two-fold: 1) to smooth out small, interannual
variability, and 2) to avoid annually changing the DMRs, thereby by providing stability for the
industry to better plan their operations. The following table outlines what has been used thus far.
Note that data from 1996-2005 form the basis for 2007-2009 monitoring.
328
10-Year Basis Period
1990-1999
1993-2002
1996-2005
Years of application
2001 - 2003
2004 – 2006
2007 - 2009
References
Clark, W. G., Hoag, S. H., Trumble, R. J., and Williams, G. H. 1992. Re-estimation of survival for
trawl caught halibut released in different condition factors. Int. Pac. Halibut Comm. Report of
Assessment and Research Activities 1992:197-206.
Kaimmer, S. M., and Trumble, R. J. 1998. Injury, condition, and mortality of Pacific halibut bycatch
following careful release by Pacific cod and sablefish longline fisheries. Fish. Res. 38:131144.
Williams, G. H. 1996. Pacific halibut discard mortality rates in the 1994 Alaskan groundfish
fisheries, with recommendations for monitoring in 1996. Int. Pac. Halibut Comm. Report of
Williams, G. H. and Chen, D. 2003. Pacific halibut discard mortality rates in the 1990-2002 Alaskan
groundfish fisheries, with recommendations for monitoring in 2004. Int. Pac. Halibut Comm.
Report of Assessment and Research Activities 2003:227-244.
329
Table 1. Groundfish target definitions and the method used to determine target species for
observer sampled hauls, as used in the halibut discard mortality rate analysis.
Target
A
B
C
F
K
L
O
P
R
S
T
W
Y
BSA
Definition
Atka mackerel
Bottom pollock
Pacific cod
Other flatfish
Rockfish
Flathead sole
Other spp.
Pelagic pollock
Rock sole
Sablefish
Greenland turbot
Arrowtooth flounder
Yellowfin sole
Target
A
B
C
D
H
K
L
O
P
S
W
X
GOA
Definition
Atka mackerel
Bottom pollock
Pacific cod
Deep water flatfish
Rockfish
Flathead sole
Other spp.
Pelagic pollock
Sablefish
Arrowtooth flounder
Rex sole
OPEN ACCESS and CDQ TARGET DETERMINATION
P
if pollock > 95% of total catch, or
W
if arrowtooth flounder ≥ 65% of total catch.
Y/R/L/F if (rock sole + other flatfish + yellowfin sole + flathead) is the largest component of the
retained catch using this rule:
Y
if yellowfin sole is ≥ 70% of (rock sole + other flatfish + yellowfin sole + flathead sole),
or
R
if rock sole > other flatfish and rock sole > flathead sole, or
L
if flathead sole > other flatfish and flathead sole > rock sole, or
F
if none of the three conditions above are met.
If target is not P, W, Y, R, L or F, then target is whichever species or species group (A, B, C, K, O,
S, or T) forms the largest part of the total catch.
Gulf of Alaska
P
if pollock ≥ 95% of total catch, or
W
if arrowtooth flounder ≥ 65% of total catch.
If target is not P or W, then target is whichever species or species group (A, B, C, D, H, K, L, O, S,
or X) forms the largest part of the total catch.
330
Table 2. Information on observer coverage, sampling, and size composition of the halibut
bycatch in 2006.
Area/Gear
No. of vsls
No. of
No. of fish
Mean
Percent Percent
/Target
observed
smpld hauls measured length (cm) <65 cm < 82 cm
BSA Longline
Pacific cod
39
5,875
10,433
67.8
42.5
86.6
Rockfish
3
20
0
Turbot
7
137
20
88.6
5.0
20.0
BSA Pot
Pacific cod
40
727
747
63.9
52.7
98.7
BSA Trawl
Atka mackerel
14
1,051
135
65.1
68.9
84.4
Bottom pollock
71
1,464
5,846
55.6
71.0
94.6
Pacific cod
65
1,908
5,720
51.6
86.6
95.9
Other flatfish
1
4
10
61.0
80.0
90.0
Rockfish
6
168
23
90.1
13.0
39.1
Flathead sole
14
842
1,930
59.0
70.1
91.7
Other sp.
1
1
0
Pelagic pollock
96
13,106
16,217
57.9
68.8
93.9
Rock sole
23
1,268
4,725
46.5
87.6
94.9
Sablefish
0
0
0
Turbot
0
0
0
Arrowtooth flndr
0
0
0
Yellowfin sole
29
2,418
2,623
58.8
66.3
78.9
GOA Longline
Pacific cod
17
658
2,021
67.4
45.4
88.5
GOA Pot
Pacific cod
24
385
489
74.0
19.6
75.5
GOA Trawl
Bottom pollock
34
435
658
64.2
55.5
85.0
Pacific cod
32
213
1,018
62.7
64.5
93.3
Dp wtr flatfish
0
0
Shall wtr flatfish
21
186
1,184
53.7
79.9
94.7
Rockfish
36
554
258
77.2
29.5
65.1
Flathead sole
12
139
414
62.0
69.6
86.5
Other sp.
3
4
0
Pelagic pollock
36
238
37
66.9
54.1
81.1
Sablefish
4
20
17
71.5
41.2
70.6
Arrowtooth flndr
18
171
352
68.0
46.9
84.9
Rex sole
5
73
241
64.7
54.4
89.2
331
Table 3. Distribution of 2006 halibut condition & injury data, by factor and open access
target fishery.
Target
BSA Trawl
Atka mackerel
Bottom pollock
Pacific cod
Other flatfish
Rockfish
Flathead sole
Other sp.
Pelagic pollock
Rock sole
Turbot
Arrowtooth flounder
Yellowfin sole
BSA Pot
Pacific cod
GOA Trawl
Bottom pollock
Pacific cod
Deepwater flatfish
Rockfish
Flathead sole
Other sp.
Pelagic pollock
Sablefish
Arrowtooth flounder
Rex sole
GOA Pot
Pacific cod
Target
BSA Longline
Pacific cod
Rockfish
Turbot
GOA Longline
Pacific cod
Exc
Raw data
Poor
Dead
DMR
Exc
Extrapolated data
Poor
Dead
DMR
SE
0.640
0.737
0.768
0.818
0.900
0.748
0.898
0.833
0.865
0.2694
0.1065
0.1003
0.1820
0.1682
0.0689
0.1176
0.1262
27
253
860
0
0
205
0
21
207
0
0
112
31
344
816
3
0
329
0
62
479
0
0
150
59
3,806
3,022
7
22
765
0
16,129
2,840
0
0
1,908
0.646
0.832
0.711
0.795
0.900
0.701
0.898
0.811
0.840
2,430
8,158
18,653
0
0
6,866
0
43
9,687
0
0
4,374
2,827
5,075
14,857 43,992
28,074 126,011
350
1,138
0
2,598
15,231 44,540
0
0
139 31,609
26,679 203,947
0
0
0
0
5,431 130,000
456
21
18
0.079
1,512
63
68
0.080
0.0250
68
376
0
291
112
53
0
10
0
67
105
69
211
0
198
59
34
0
4
1
55
38
453
293
0
542
87
79
0
23
16
149
52
0.778
0.517
0.635
0.516
0.605
0.673
0.879
0.656
0.455
1,498
9,264
0
5,307
7,117
2,069
0
49
0
1,799
1,624
1,408
5,892
0
5,182
2,505
1,198
0
15
17
2,109
860
4,832
9,890
0
17,103
4,427
3,707
0
100
473
9,836
737
0.701
0.559
0.700
0.483
0.632
0.659
0.888
0.755
0.454
0.2363
0.0581
0.1068
0.1003
0.1200
0.1276
0.4509
0.1992
0.1955
411
43
34
0.158
1,215
120
89
0.147
0.0728
Raw data
Mod Severe Dead
DMR Minor
8,753
0
16
1,042
0
4
250
0
0
207
0
0
0.103 212,411 23,341
0
0
0.101
215
38
5,689
0
0
1,652
259
37
73
0.123 78,538 12,794
1,956
Minor
332
Extrapolated data
Mod Severe Dead DMR
SE
4,438
0
0
0.098
0.084
0.0184
0.0254
3,756
0.128
0.0446
333
Gear/Target
BSA Trawl
Atka mackerel
Bottom pollock
Pacific cod
Other Flatfish
Rockfish
Flathead sole
Pelagic pollock
Rock sole
Sablefish
Turbot
Arrowtooth fldr
Yellowfin sole
BSA Pot
Pacific cod
BSA Longline
Pacific cod
Rockfish
Sablefish
Turbot
77
74
64
75
67
82
79
66
55
88
4
23
55
32
30
66
68
68
80
65
85
64
46
69
83
12
19
17
14
15
21
14
11
12
71
78
69
76
69
85
78
83
17
6
13
10
4
69
78
67
69
69
85
76
26
80
15
23
38
14
10
73
80
64
61
75
67
80
76
20
58
81
14
9
10
73
73
71
68
68
62
79
73
75
77
12
20
15
7
83
79
70
67
72
66
83
74
70
76
11
4
22
4
85
72
67
71
71
57
87
77
75
80
11
52
18
13
77
80
66
78
56
70
86
79
86
82
12
17
9
81
74
69
63
81
79
87
81
90
70
78
12
12
14
13
77
67
69
76
89
74
88
75
60
74
77
12
10
6
6
73
74
69
81
85
69
89
77
68
74
10
4
23
5
85
78
69
77
73
60
90
83
75
77
8
7
6
67
65
67
79
84
69
89
82
67
67
81
10
4
7
63
73
70
80
68
70
88
85
31
67
86
8
6
3
67
79
81
65
79
83
90
84
82
90
85
10
8
8
64
74
77
82
90
75
90
83
87
‘90 ‘91 ‘92 ‘93 ‘94 ‘95 ‘96 ‘97 ‘98 ‘99 ‘00 ‘01 ‘02 ‘03 ‘04 ‘05 ‘06
11
17
13
7
76
74
70
74
76
70
88
80
75
70
75
80
Used in bycatch
mgmt 2007-9
Table 4. Summary of halibut discard mortality rates (DMRs) in the open access (non-CDQ) Bering Sea/Aleutian
(BSA) groundfish fisheries during 1990-2006.
334
Gear/Target
GOA Trawl
Atka mackerel
Bottom pollock
Pacific cod
Deep wtr flats
Shall wtr flats
Rockfish
Flathead sole
Pelagic pollock
Sablefish
Arrowtooth fldr
Rex sole
GOA Pot
Pacific cod
GOA Longline
Pacific cod
Rockfish
Sablefish
18
27
7
12
15
6
17
89
62
62
58
71
75
82
60
-
67
51
60
61
66
65
71
70
-
13
28
16
81
66
66
70
69
79
72
68
-
7
7
30
24
67
57
59
59
65
75
63
59
-
11
22
17
53
48
53
60
62
58
54
61
67
56
13
4
-
21
66
64
56
70
71
64
51
58
76
11
13
-
7
60
79
70
71
71
65
67
81
80
66
63
22
-
11
66
62
61
71
63
74
70
61
48
47
11
9
-
16
55
64
51
67
68
39
80
62
58
17
-
13
55
54
51
81
74
51
86
68
73
70
16
9
-
8
52
57
62
67
71
69
80
38
75
71
11
-
33
58
67
49
62
61
68
89
66
86
62
11
-
19
55
59
48
66
64
74
90
62
76
57
13
-
21
47
69
31
80
65
49
34
70
69
16
-
22
73
63
49
71
73
62
88
79
65
67
8
-
13
45
66
77
66
57
62
66
61
13
-
15
70
56
70
48
63
66
89
76
45
‘90 ‘91 ‘92 ‘93 ‘94 ‘95 ‘96 ‘97 ‘98 ‘99 ‘00 ‘01 ‘02 ‘03 ‘04 ‘05 ‘06
14
10
-
16
60
59
63
53
71
67
61
76
65
69
63
Used in bycatch
mgmt 2007-9
Table 5. Summary of halibut discard mortality rates (DMRs) in the open access Gulf of Alaska (GOA) groundfish
fisheries during 1990-2006.
Table 6. Observer coverage and halibut viability/injury data collected from the 2006 Bering Sea/
Aleutian Community Development Quota (CDQ) fisheries.
Target
CDQ Trawl
Atka m.
Btm pol
Rockfis
Pel pol
Rocksol
YF sole
Raw Data
Extrapolated data
No. of # of
Exc./ Poor/ Dead/
Exc./ Poor/ Dead/
Vsls Hauls Minor Mod. Sev. Dead DMR Minor Mod. Sev. Dead DMR
3
11
3
12
3
3
147
76
39
1,684
160
199
8
13
2
3
4
0
6
25
5
9
44
29
26
258
10
686
201
202
4
508
146
14
55
CDQ Longline
P cod
20
1,780
1,629
354
32
CDQ Pot
Sable
-
23
471
417 3,104
82
198
41 1,996
662 12,038
809 7,395
-
0.798
0.876
0.690
0.895
0.862
0.730
SE
0.708
0.840
0.715
0.892
0.827
0.856
70
152
2
10
58
0
0.2101
0.2853
0.3640
0.0266
0.1664
0.1759
- 0.321
430
41
183
- 0.404 0.2537
39 0.120 32,758
6,007
695
821 0.104 0.0370
Table 7. Summary of halibut discard mortality rates (DMRs) in the Community Development Quota
(CDQ) Bering Sea/Aleutian (BSA) groundfish fisheries during 1998-2006.
Gear/Target
CDQ Trawl
Atka mackerel
Bottom pollock
Rockfish
Flathead sole
Pelagic pollock
Rock sole
Yellowfin sole
CDQ Pot
Sablefish
CDQ Longline
Pacific cod
Turbot
1998
1999
2000
2001
2002
2003
2004
2005
2006
Mean DMR
1998-2006
90
90
-
82
88
88
90
83
89
90
83
88
-
80
90
90
90
89
-
90
66
89
81
86
90
89
87
84
90
88
89
90
90
88
80
88
69
90
86
73
85
86
82
87
90
86
84
-
-
38
46
25
22
18
56
40
35
10
-
10
-
13
4
11
-
9
-
9
-
9
-
10
-
10
-
10
4
335
Table 8. Recommended Pacific halibut discard mortality rates (DMRs) for 2008 CDQ
fisheries.
CDQ Fisheries
Recommended
Gear/Target
DMR
Trawl
Atka mackerel
85
Bottom pollock
86
Rockfish
82
Flathead sole
87
Pelagic pollock
90
Rock sole
86
Yellowfin sole
86
Pot
Sablefish
34
Longline
Pacific cod
10
Turbot
4
336
Halibut bycatch limits in the 2007 Alaska groundfish fishery
Gregg H. Williams
Abstract
Bycatch of Pacific halibut in the groundfish fisheries off Alaska has been managed with
Prohibited Species Catch limits. In 2007, the limits totaled 2,300 t (3.80 Mlbs net) in the Gulf
of Alaska and 4,575 t (7.58 Mlbs net) in the Bering Sea. The limits are annually set by the North
Pacific Fishery Management Council, and are subdivided by gear types, target fisheries and time
period. In contrast to other bycatch species, the halibut limits are set as estimated mortality rather
than total catch.
Introduction
This document summarizes the 2007 groundfish fishery off Alaska and the accompanying
bycatch of Pacific halibut. All of the federally-managed groundfish fisheries off Alaska were
managed with mortality limits, although certain gear types were exempted to encourage their use.
If reached, a limit would have closed a fishery before the Total Allowable Catch (TAC) of the
target species was attained.
2007 halibut bycatch limits and fishery closures
Tables 1 and 2 show the halibut mortality limits for the groundfish fisheries in the Gulf of Alaska
(GOA) and Bering Sea/Aleutians (BSA) as adopted by the North Pacific Fishery Management
Council (Council). As in previous years, the Council apportioned the trawl and fixed gear limits
into seasonal or quarterly amounts. NMFS took actions later in the year to reassign portions of
the limits from fisheries that were closed to fisheries that were running short of their limit. NMFS
management areas are shown in Figures 1 and 2.
Gulf of Alaska
For the GOA, the Council used a framework approach to set the trawl limit of 2,000 t (3.3
Mlbs net) (Table 1). As in previous years, the GOA trawl limit was divided between the fisheries
for shallow water and deep water complexes by specific season. However, the fifth seasonal
apportionment (October 1 through December 31) was not divided between the complexes.
Bycatch management in the GOA hook-&-line fishery in 2007 was similar to previous years.
The bycatch limit was set at 300 t (0.5 Mlbs net) for all other fixed gear fisheries, which was an
amount similar to bycatch levels of past years for those fisheries. The fixed gear fisheries targeted
primarily on Pacific cod in the central and western GOA during the winter, and rockfish in the
eastern GOA in the spring. All pot and jig gear fisheries were exempted from mortality limit, as
well as the sablefish IFQ fishery.
Halibut bycatch mortality limits for the 2007 BSA trawl and fixed gear fisheries are listed
in Table 2. The list represents fishery categories defined and implemented by BSA Fishery
337
Management Plan (FMP) Amendment 21. Limits for the individual fisheries were based on “need”,
as recommended by industry representatives and adopted by the Council. The bycatch limits were
apportioned by quarter or season. When a limit was reached, the entire BSA was closed to further
fishing until the next season, or for the remainder of the year. Bycatch limits for most trawl fisheries
in 2007 were very similar to those established in 2006, although some minor changes occurred.
As in past years, the BSA fixed gear fisheries were initially allocated a bycatch limit of 900
t but 7.5% was reassigned to Community Development Quota (CDQ) fisheries, leaving a total of
833 t. The Pacific cod hook-&-line limit was divided into three seasonal apportionments, with
the summer apportionment intentionally “zeroed out” to eliminate any cod fishing during the
traditionally high-bycatch period. All pot and jig fisheries were exempted from halibut mortality
closures. The sablefish IFQ hook-&-line fishery was also exempted from the bycatch limit.
In 2007, the CDQ program operated throughout the year. Under the program, 10 percent
of the pollock TAC and 7.5 percent of all other groundfish TACs were allocated to the six CDQ
programs. Ten percent of the trawl bycatch limit and 7.5% of the hook-&-line bycatch limit was
allocated to the CDQ program, with it subdivided among the six CDQ programs in relation to their
groundfish allocations.
338
Table 1. Halibut bycatch mortality limits (metric tons, round weight) for the 2007 Gulf of
Alaska groundfish fisheries. Exempted fisheries for 2007 include groundfish pots, jigs, and
the IFQ hook-&-line fishery for sablefish.
Gear/Time Period
Trawl
Shallow water complex1
January 20 – March 31
April 1 – June 30
July 1 – September 1
September 1 – October 1
October 1 – December 31
Bycatch Limit (t)
2,000
450
100
200
150
Remainder - no apportionment
Deep water complex2
April 1 - June 30
July 1 – September 1
September 1 – October 1
October 1 – December 31
100
300
400
Any rollover
Remainder - no apportionment
Hook-&-Line
All species except demersal shelf rockfish and sablefish
January 1 – June 10
June 10 – September 1
September 1 – December 31
Demersal shelf rockfish (Southeast only)
300
250
5
35
10
Groundfish Pots & Jigs
GRAND TOTAL
Exempt
2,300
Shallow water complex: pollock, Pacific cod, shallow water flatfish, flathead sole, Atka mackerel, and other species.
Deep water complex: rockfish, sablefish, deep water flatfish, and arrowtooth flounder.
1
2
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Table 2. Halibut bycatch mortality limits (metric tons, round weight) for the 2007 Bering
Sea/Aleutian Islands groundfish fisheries. Exempted fisheries for 2007 include groundfish
pots, jigs, and the IFQ hook-&-line fishery for sablefish.
Fishery group
Bycatch Limit (t)
Trawl
Yellowfin sole
April 1 – May 20
May 21 – June 30
July 1 – December 31
936
312
195
49
380
Rock sole/flathead sole/other flatfish
April 1 – June 30
829
498
164
167
Turbot/sablefish/arrowtooth flounder
n/a
Rockfish
69
69
Pacific cod
1,334
Pollock/Atka mackerel/other species
Total Trawl Mortality Limit
232
3,400
Fixed Gear
Hook-&-line Pacific cod
January 1 – June 10
June 10 – August 15
August 15 – December 31
775
320
0
455
Other hook-&-line1
May 1 – December 31
58
Groundfish Pot & Jig
Total Fixed Gear Mortality Limit
Exempt
833
CDQ Fisheries (trawl and hook-&-line)
342
GRAND TOTAL
4,575
For all practical purposes, this only includes rockfish and turbot. The sablefish IFQ fishery was exempt from the 2007
bycatch limits.
1
340
Figure 1. NMFS statistical (3-digit) and management areas for the Gulf of Alaska.
341
Figure 2. NMFS statistical areas for the Bering Sea/Aleutians.
342
The Bering Sea trawl fishery Prohibited Species Donation
Program: Results from 1998-2007
Gregg H. Williams
Abstract
Since 1998, SeaShare of Bainbridge Island, Washington has operated a program which
acquires unintentionally-landed halibut bycatch in Alaska for donation to hunger relief programs.
The program is conducted under a Prohibited Species Donation (PSD) program adopted by the
National Marine Fisheries Service (NMFS) and the North Pacific Fishery Management Council
(Council) following several years of development and, ultimately, approval by the International
Pacific Halibut Commission (IPHC). In 2007, halibut collected for this program totaled 36,619
pounds (preliminary) and were landed by shore-based catcher vessel trawlers at two participating
processors in Dutch Harbor. Donations in the program have totaled 230,457 pounds (net weight)
since program inception. NMFS Enforcement Division has monitored the halibut donated to this
PSD program and has reported no incidents.
Final 2006 results
The amount of halibut collected by SeaShare in 2006 was 10,762 pounds, with two participating
processors (Table 1). As in past years, Unisea was the leading contributor, followed by Alyeska.
Processing and inspection was conducted by SeaFreeze personnel, as in previous years. Food
Lifeline in Seattle was one of the recipients of the processed halibut
Preliminary 2007 results
As in past years, two Dutch Harbor processors (UniSea and Alyeska) participated in 2007.
As of November 27, 2007, 34,619 pounds (net weight) of frozen, headed & gutted halibut had
been received (Table 1): 69 percent from Unisea and 31 percent from Alyeska. The total amount
processed increased substantially from 2006, and was attributed to Unisea. SeaShare officials noted
that while most of the fish came in during the latter half of 2007, both companies accumulated fish
as it was received and stored it in their freezers. Shipment occurred when needed, so the fish could
have been in the freezer for several months. Also, a late summer visit to Dutch Harbor by SeaShare
officials may have created renewed interest in the program and spurred an increase in donations.
Handling of fish was similar to past years. The fish were delivered to SeaFreeze in Seattle
through shipping that was donated by Coastal Transportation. SeaFreeze weighed the halibut in
the totes, and the net weight was estimated. The fish were processed in Seattle into steaks, then
sleeved, and repackaged for delivery. Halibut steaks were distributed to food banks in San Jose
and Oakland, CA.
Program history
The initial program adopted by the Council in 1998 expired on December 31, 2000. NMFS
and IPHC staff conducted a review of the program during 2000 for the purpose of examining the
343
appropriateness of extending the program. The review was discussed with the Council at its June,
2000 meeting and formed the basis of an extension of the program. The extension contains no
sunset provision but does require a review every three years. Although limited to shore-based trawl
catcher vessels that land in Dutch Harbor, there is neither a limitation on the amount that can be
donated nor a requirement that the halibut bycatch originates from specific fisheries.
Table 1. Amount of halibut (pounds, net weight) received and distributed by SeaShare through
the NMFS Prohibited Species Donation program since program inception in 1998.
Year
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
Total
UniSea
10,498
3,762
Alyeska
10,698
714
Westward
---
Total
21,196
4,476
6,534
32,318
33,256
15,737
14,274
27,340
7,415
32,261
183,395
5,051
10,281
718
2,669
1,616
1,946
3,347
2,358
39,398
6,684
980
------7,664
18,269
43,579
33,974
18,406
15,890
29,286
10,762
34,619
230,457
344
Biological Research
345
346
Examination of genetic population structure in spawning
adults of Pacific halibut: laboratory and field work completed
in 2007
Lorenz Hauser
University of Washington, College of Ocean and Fishery Sciences
Timothy Loher
International Pacific Halibut Commission
James Rhydderch and Lyndsay Newton
University of Washington, College of Ocean and Fishery Sciences
Abstract
The eastern north Pacific halibut resource is presently managed under the assumption that
a single fully mixed population exists from California through the eastern Bering Sea. This
belief rests largely upon studies that indicate that drift of larvae to the northwest is balanced by
migration of juveniles and adults to the southeast, over broad geographic expanses. In 2002, a
project was initiated to investigate genetic population structure in the northeast Pacific, and in
2004 the study was expanded to spawning groups from British Columbia, the central Gulf of
Alaska, and southeast Bering Sea. Although initial analysis suggested population differentiation,
interpretation of results was complicated by very low FST values and the fact that genetic studies
conducted without temporal replicates are in danger of detecting false positives. Here, we report
results of 2007 winter charters that resample locations visited in 2004, and present data from 13
microsatellite loci from spawning halibut collected in 2004 (Pribilof Canyon, Portlock Bank, and
the Queen Charlotte Islands) and historical samples from 1998 (the Queen Charlotte Islands and
Portlock Bank). Three longline vessels were chartered during February of 2007. Mature fish were
sampled at all sites, with males captured at higher rates than females. Samples were collected
from 100 mature males and 99 mature females at the Queen Charlotte Islands, 100 males and
200 females at Portlock Bank, 99 males and 100 females at Pribilof Canyon, and 158 males and
100 females in the Aleutian-Andreanof Islands. Using samples collected prior to 2007, analyses
of sexes combined suggest differentiation of Pribilof Canyon from Portlock Bank and the Queen
Charlotte Islands when temporal samples are pooled. Increasing the number of loci analyzed
changed results surprisingly little from prior work, though increasing sample sizes did result in
increased levels of significance. Suggestions for future research include screening of remaining
samples, filling gaps in the current data set, and pursuing markers such as mitochondrial DNA and
microsatellites in evolutionarily selected genes.
Introduction
The idea that fisheries management should be based on local self-sustaining populations rather
than the typological species can be traced back to the turn of the 19th century (Heincke 1898, Hjort
347
1914). Fisheries models developed since then are based on fish “stocks”, which are the unit for the
estimation of parameters such as the number of spawning individuals and recruitment (Hilborn and
Walters 1992). Despite this long history of the stock concept (Sinclair 1988, Carvalho and Hauser
1994), our knowledge of the population structure of many marine species is still very limited,
not only because of the apparent lack of environmental barriers to dispersal, but also because
the ecology and life history of many species seems to promote large scale dispersal (Hauser and
Ward 1998). Furthermore, early molecular studies based on protein variability often revealed
little genetic differentiation, suggesting the existence of large panoceanic populations. However,
the recent combination of improved sampling designs and more sensitive genetic markers has
provided evidence for population structure on a surprisingly small scale (e.g. cod; Ruzzante et
al. 2000, Hutchinson et al. 2001), and allowed the identification of stocks relevant to fisheries
management.
An example for a species with uncertain population structure is Pacific halibut (Hippoglossus
stenolepis), which are distributed in the North Pacific from northern California through the northern
Sea of Japan, and within the Bering Sea north to Norton Sound and the Gulf of Anadyr (Hart
1988). The species has long represented an important fishery resource in western North America,
being fished by the indigenous peoples of the US and Canada for hundreds of years and by a
commercial fleet since the late 1880’s (IPHC 1998). Over the last decade, commercial catches in
the US and Canada have fluctuated around an annual mean of ~50 million pounds (IPHC 2007).
The value of this resource is recognized throughout the region, as evidenced by the establishment
of the International Pacific Halibut Commission (IPHC) in 1923 by the governments of the US and
Canada to jointly manage and study the eastern Pacific population(s).
Presently, the eastern Pacific halibut resource is managed under the assumption that a single
fully mixed population exists from California through the eastern Bering Sea. This belief rests
largely upon a long history of tagging studies (see review in Kaimmer 2000) and analyses of larval
distribution (Skud 1977, St. Pierre 1989) indicating drift of larvae to the northwest, throughout
the Gulf of Alaska and into the Bering Sea, balanced by migration of juveniles and adults to
the southeast, over broad geographic expanses. In particular, individuals tagged in the southeast
Bering Sea have been recovered as far south as California, and maximum annual movements of
over 1,500 km have been observed (Skud 1977). Thus, Pacific halibut in the eastern Pacific Ocean
are treated as a single unit stock with regard to reproduction and recruitment, while management
is conducted within a series of Regulatory Areas. The Gulf of Alaska fishery was historically
separated into two broad regulatory regions located east and west of Cape Spencer, Alaska. This
division was originally based on differences in size- and age-structure within the stock as well as
tagging studies that suggested adult fish move more freely within regulatory areas than between
them (Thompson and Herrington 1930, Van Cleve and Seymour 1953). Regulatory areas have
become progressively smaller and more numerous but recent analyses indicate that population
dynamics may differ between the Bering Sea and Gulf of Alaska(Clark and Hare 2001). However,
the Bering Sea population component is effectively treated as an extension of the Gulf of Alaska.
While the management scenario rests upon the best available information regarding movements
and spatial population structure, there is reason to believe that actual structure could be more
complex than presently understood. Conclusions drawn from tagging studies are sensitive to
patterns of fishing effort, tag loss, and reporting (Hilborn et al. 1995). Patterns observed in size
structure and abundance between regions can be caused by factors other than reproductive isolation,
such as regional differences in mortality or responses to environmental conditions. In light of this,
348
attempts have been made to identify reproductive units using a variety of genetic techniques. Use
of allozyme electrophoresis (Tsuyuki et al. 1969, Grant et al. 1984) has generally not demonstrated
significant genetic variation within the eastern north Pacific, though significant genetic separation
between the eastern and western Pacific has been identified (Grant et al. 1984). More recent
research using nuclear DNA microsatellites supported the hypothesis that eastern and western
Pacific stocks are genetically separate, but also suggested that the eastern Pacific population may
“be structured in distinct reproductive groups” (Bentzen et al. 1998). In particular, the results of
existing genetic analyses are difficult to interpret due to a number of study limitations, and the
true nature of the relationship between population components within the Bering Sea and Gulf of
Alaska remains elusive.
In 2002 the IPHC embarked upon a renewed effort to examine genetic population structure
in halibut, using markers (nuclear microsatellites) that are theoretically more powerful than
those previously employed, and seeking to remedy sampling problems that have hampered
historical studies. The initial phase of the project was completed in 2003, intended simply to
screen microsatellites and optimize laboratory conditions for future work. Samples collected
from commercial landings at St. Paul Island (AK), Adak Island (AK) and Newport (OR) were
tested for evidence of genetic differentiation at 10 microsatellite loci. This study provided some
evidence for low-level differentiation among populations, but was limited by unsuitable samples.
These samples were collected in summer, and therefore represented individuals in non-spawning
condition, potentially far away from their spawning groups. Studies suggest that halibut may carry
out extensive migrations between shallow water summer feeding and winter spawning grounds
located near the shelf edge (Loher and Seitz 2006, Seitz et al. 2007) and subsequently home
to their summer feeding grounds (Loher 2007). Such migrations have also been supported by
seasonal changes in the overall distribution of mature fish (Skud 1977, St. Pierre 1984). Samples
collected in summer may therefore represent population mixture and be unsuitable for the analysis
of population differentiation.
We subsequently extended the scope of this project using samples collected from spawning
aggregations (Hauser et al. 2006). Additional loci were screened for variability, ease of scoring
and reliability. In addition to the loci from Atlantic halibut that were available for the previous
study (McGowan and Reith 1999, Coughlan et al. 2000), additional Atlantic halibut loci became
available from the publication of a more recent population genetics study (Reid et al. 2005). We
reported data from ten loci of 96 individuals from each of the three samples. Although this data
set was very powerful for population genetic data analysis, studies conducted without temporal
replicates are in danger of detecting false positive results (Waples 1998) and therefore samples
should be collected over several years. In 2007, we extended the project by increasing the number
of loci screened to 13, and included two historical collections from spawning populations: one
from near the Queen Charlotte Islands, British Columbia, and one from Portlock Bank, Alaska. In
addition, winter charters were conducted to resample the spawning grounds visited in 2004, and
obtain a sample from the Aleutian Islands that will allow us to expand the geographic scope of
the analysis. This report details those collections and results-to-date of the temporally expanded
microsatellite analysis.
349
Methods
Field work: 2007 winter charters
Sampling locations, vessels, and timing
Four charter regions were visited (Fig. 1), two in the Gulf of Alaska (the Queen Charlotte
Islands and Portlock Bank), one in the southeast Bering Sea (Pribilof Canyon), and one in the
Andreanof Islands. Fishing was not confined to specific set locations in any region. For the first
three regions, vessels were allowed to fish anywhere within established rectangular boundaries
that corresponded to the boundaries established in 2004. For the Andreanof region, the vessel
was allowed to fish anywhere west of 172º W longitude. Within these general regions the captain
of the vessel, in coordination with Commission staff, was allowed to “prospect” in order to find
aggregations of spawning adult fish, targeting high catch regions in order to complete sets during
the good weather periods. Charter specifications stipulated that for the first three charter regions
all fishing was to be conducted between January 10 and February 21. The Andreanof region could
be fished until February 28. These periods correspond to the peak in known spawning activity (St.
Pierre 1984).
The Queen Charlotte Islands region was chosen to represent the southernmost known major
spawning location in the Gulf (St. Pierre 1984). The region was defined by the following boundaries:
between 54º 30’ and 51º 30’ north latitude, and between 134º 00’ and 130º 00’ west longitude. This
charter region was awarded to the F/V Banker II from Queen Charlotte City, British Columbia. The
Banker II is a 50’ longline vessel with winter fishing experience in the sablefish and deep-water
rockfish fisheries. The vessel began official charter operations on February 10 and completed
charter obligations on February 12, having actively fished for two days, fishing overnight to avoid
incoming weather.
The Portlock region, east of Kodiak Island, represented the center of the Gulf and was defined
as the grounds between 59º 15’ and 57º 00’ north latitude, and between 151º 00’ and 148º 00’ west
longitude. The Portlock charter was conducted by the F/V Predator from Homer, Alaska. The
Predator is a 59’ longline vessel experienced with winter Pacific cod and crab fishing. The vessel
began official charter operations on February 1 and completed charter obligations on February 12,
having actively fished on five days after a four-day initial weather delay.
The Pribilof Canyon region, in the southeast Bering Sea, was chosen to represent the northernmost
known major spawning ground (St. Pierre 1984). It was defined as falling between 56º 25’ and 55º
15’ north latitude, and between 171º 00’ and 168º 00’ west longitude. This region was awarded
to the F/V Kema Sue of Kodiak, Alaska. The Kema Sue is an 80’ longliner with an enclosed,
heated shelter deck, extensive experience in the midwinter Pacific cod fisheries of the northern
Gulf of Alaska and Bering Sea, and the vessel that conducted the 2004 IPHC winter charter in the
same region. The vessel began official charter operations on January 25 and completed charter
obligations on February 12, having actively fished for three days after a 13-day pre-fishing transit
period from Kodiak to the grounds, including weather delays.
In addition, the Commission sought to find a vessel to fish in the Andreanof Islands, defined
as falling between 51º 30’ and 52º 30’ north latitude, and between east of 177º 00’ and 172º 30’ west
longitude. No vessels bid on this charter opportunity, but upon being awarded the Pribilof Canyon
charter, the owners and captains of the F/V Kema Sue agreed to fish the region at the end of their
available charter window, providing that the objectives at Pribilof Canyon could be accomplished
350
no later than February 16. The vessel began the Aleutian charter leg on February 13 and completed
fishing the site on February 26, after which a 15-day offload and transit period, including weather
delays, was required before the vessel arrived at the port of Kodiak.
Sampling gear
Because these charters were conducted solely for the purpose of sample collection and not to
assess relative abundance among areas, vessels were allowed to fish whatever gear configuration
best suited their operations. All vessels employed benthic longline gear comprised of 1,800’
skates. Hook size, spacing, gangion length, and bait varied among vessels. The Banker II used
snap gear with a mix of size 14/0 and 15/0 circle hooks on 1’ gangions at a 9’ spacing, baited with
chum salmon, and a 5-10 lb weight at each skate change. The Predator used 16/0 circle hooks at
10’ spacing, baited with cut salted herring. The Kema Sue used fixed gear, with size 16/0 circle
hooks on 2-3’ gangions at an 18’ spacing, baited with a combination of squid and walleye pollock.
Sash weights were placed between skates while fishing in the Andreanofs, but not at Pribilof
Canyon. Vessels were staffed by the captain, a crew of two or three additional mates, and two
IPHC biologists (Table 1).
Sample handling and analysis
Upon capture, the gonads of each fish were removed to assess sex, and a maturity stage was
assigned based on gonad characteristics as per standard IPHC setline survey protocols (IPHC
2004). Fork length (FL) was then measured and recorded, and otoliths were removed using
relatively clean techniques that avoided contact between the otoliths and metal objects. Steel
knives were used to cut and pry open the otolith cavity, but samplers took care to ensure that no
contact occurred between the knife and the otoliths. Once exposed, otoliths were removed using
plastic- or ceramic-tipped forceps, cleaned using freshwater, and placed in dry plastic storage trays
without the use of glycerin solution. Tissue samples (fin clips) were collected from fish deemed to
be sexually mature, with tissue sampling terminating after 100 fish of each sex had been sampled.
Clips of about 0.5 cm2 were taken either from the tip of the tail or the pectoral fin and immediately
preserved in 100% ethanol. Vessels were also equipped with electronic PIT tag scanning gear
(Forsberg 2003), and all fish captured were scanned either during onboard processing or offload
in order to check for the presence of PIT tags. At the end of each charter, all tissue and otolith
samples were shipped to the IPHC’s Seattle office for future analysis.
Lab work: expanded population analysis
Samples
Three samples of spawning adults were collected in 2004, one each at the Queen Charlotte
Islands (BC, Canada; QCI), Portlock Bank (Gulf of Alaska; PTL) and Pribilof Canyon (Bering
Sea; PBC) (Fig. 1; Loher 2005). Two additional samples, collected in 1998, were available from
winter charters conducted in Dixon Entrance (Queen Charlotte Islands) and on Portlock Bank.
Ninety-six individuals, 48 males and 48 females, were chosen from each sample and used for
genotype determination at 13 loci (Table 2). In total, we therefore screened 480 fish at 13 loci.
Genotyping
PCR reactions contained 10 mM Tris-HCl pH 8.5, 50mM KCl, 0.1% Triton X-100, 800 µM
dNTPs, 0.5 units Taq DNA polymerase, variable concentrations of MgCl2 and primers (Table 2),
351
and water to bring the total volume of the reaction to 10 µL. An initial denaturation step of 95ºC
for 2 min was followed by either 25 or 30 cycles of 95º C for 30 s, the annealing temperature (Table
2) for 30 s, and 72ºC degrees for 30 s, followed by a final extension step at 72ºC for 40 min. Six
loci were screened using a method requiring only a single labeled M13 primer (Schuelke 2000):
one of the primers has a 5-prime extension complementary to the M13 primer. The advantage of
this method is considerable savings, in that only a single labeled primer needs to be purchased
instead of specific labeled primers for each locus.
Samples
Analyses were carried out on samples with sexes separately as well as sexes combined.
Microchecker (Van Oosterhout et al. 2004) was used to check for scoring problems such as large
allele dropout and stuttering. Exact tests were used to test for deviations from Hardy-Weinberg
and linkage equilibrium (GENEPOP; Raymond and Rousset 1995). Genic and genotypic tests for
population differentiation were carried out by exact tests (GENEPOP v 3.4; Raymond and Rousset
1995), G-test based permutation tests (FSTAT v 2.9.3; Goudet 1995) and FST based permutation
tests (GENETIX v4.05; Belkhir et al. 2004). Genotypic tests in FSTAT and tests in GENETIX
were based on complete multilocus genotypes. All individuals with missing data were excluded,
resulting in smaller samples sizes and lower power. F statistics were calculated following Weir and
Cockerham (1984) in FSTAT v 2.9.3 (Goudet 1995). Multidimensional Scaling Plots were produced
in SPSS from pairwise FST values. Negative FST values were set to zero before analyses.
Results
Field work: 2007 winter charters
Mature halibut of both sexes were successfully captured and sampled in all charter regions
(Table 3). Catches varied among areas and the charter contracts specified that each vessel’s charter
obligation would be fulfilled under slightly different conditions. The Queen Charlotte Islands
and Portlock charters were established as lump-sum contracts wherein the vessel’s obligation was
considered fulfilled when tissue samples and otoliths had been collected from 100 adult male and
100 adult female fish, the IPHC’s lead biologist deemed the potential for additional catch to be
negligible, or catches were so close to the target that incurring additional fishing days was deemed
unduly onerous by the project Principal Investigator (T. Loher). The specifications for the Pribilof
Canyon region were similar, but with the caveat that the vessel was chartered on a daily-rate basis
with a fixed date upon which the vessel would return to port, regardless of the total catch to date.
The Andreanof region was largely opportunistic. The vessel owners and captains agreed to fish the
region at a daily-rate following completion of the Pribilof Canyon region, provided that enough
time remained between completion of Pribilof Canyon and the end of February to allow the vessel
to return to Kodiak in time to participate in its March fishing obligations. Thus, total sample sizes
varied by region (Table 3).
Total fishing effort required to complete sampling was highest at the Andreanof Islands, where
the crew of the Kema Sue made eleven sets of gear comprised of a total of 80 skates, resulting
in 3.2 samples retrieved per skate. Catch rate was quite similar at Pribilof Canyon, where eight
sets comprised of 61 skates yielded 3.3 samples per skate. At Portlock Bank, catch rates were
roughly double that experienced in the Bering Sea: eleven sets comprised of 47 skates produced
6.4 samples per skate. Sampling proceeded most rapidly at the Queen Charlottes, where a catch
352
rate of 13.3 samples per skate required fishing just three sets comprised of a total of 15 skates to
complete the charter requirements.
In all regions, adult male halibut were captured at a higher rate than females, as was the case at
these sites during the 2004 winter charters. A total of 200 mature males were sampled at Portlock,
158 at the Andreanof Islands, 100 at the Queen Charlotte Islands, and 99 at Pribilof Canyon. Catch
of mature females was essentially equivalent at all sites; 100 samples were obtained at each site,
but one fish sampled at the Queen Charlotte Islands was immature. The majority of males sampled
in all regions were <100 cm, whereas the majority of females were between 90 and 140 cm. This
was similar to the size-distribution encountered during the winter of 2004. Age distribution of the
fish is not presently known because otoliths have not yet been subjected to age-reading. Aging of
these samples is expected to take place early in 2008. Tissue samples from the Andreanof region
will be subjected to analysis of nuclear microsatellite frequencies late in 2007, in order to complete
the population analysis using these markers. Samples from the other sites will be retained for
future analyses using alternative genetic markers.
Lab work: expanded population analysis
In total, 6279 genotypes were obtained, with an average of 40 individuals of each sex screened
at each locus (total of 392 individuals; Table 4). The quality of genotypes was generally good,
and there was no evidence of scoring errors due to stuttering or large allele drop-out. Genetic
variability was high, with an average heterozygosity over all samples and loci of 0.912, and an
average of 13.6 alleles per locus.
Exact tests for genic differentiation at 11 loci (Table 5) provided some indication for geographic
differentiation, with all three computational approaches (FSTAT, GENEPOP, GENETIX)
providing qualitatively similar results (Table 6). Although differentiation among all samples was
not significant (Fig. 2), pooling of 1998 and 2004 samples from the same location (RYP98+QCI04,
HER98+PTL04) resulted in weak but significant overall differentiation supported by two loci.
Pairwise tests for differentiation suggested genetic differences between Portlock Bank and the
Pribilof Canyon (Table 7). This differentiation is also apparent on the multidimensional scaling
plots based on FST values (Fig. 3).
Discussion
The interpretation of the analyses of population differentiation are complicated by the fact
that FST values (Fig. 2) were quite low, and sometimes negative, but still indicated differentiation
between Pribilof Canyon and Portlock Bank (Tables 5, 7). Interestingly, increasing the number of
loci from our prior report had little effect on overall results, whereas increasing sample sizes by
pooling temporal samples showed some significant differentiation. It may therefore be advisable
to screen the rest of the samples that have already been collected. Furthermore, as genotypic
tests are sensitive to missing data, it would be important to fill gaps in the current data set. In the
near future, extending the geographic scope of the survey to include the Aleutian Islands west of
Amchitka Pass may be also be pertinent, as would be the inclusion of samples from outside of the
range, such as the western Bering Sea and even samples from a population of Atlantic halibut.
In addition, we suggest two primary avenues of further research. We suggest using mitochondrial
DNA (mtDNA) as an additional marker. MtDNA is maternally inherited, and so could provide
evidence of sex-biased migration. Although it may seem unlikely that such sex-biased dispersal
353
determines levels of population structure in a species with extensive larval dispersal such as
halibut, preliminary screening of mtDNA would be fairly rapid and cost-effective. Additionally,
all the markers screened so far are selectively neutral and thus evolve primarily by homogenizing
migration (presumably extensive in halibut) and differentiating genetic drift (presumably very
small in the large halibut populations). Recent studies isolated microsatellites from expressed
genes (expressed sequence tags, ESTs) and already have shown higher differentiation in such ESTderived microsatellites than in conventional markers (Vasemägi et al. 2005). Microsatellites are
surprisingly common in ESTs, and in a recent trial in our lab, we found over 1,500 microsatellites
in 65,000 ESTs of Atlantic cod. Currently, 17,771 ESTs are available for Atlantic halibut, and it is
likely that dozens of selected markers for Pacific halibut could be obtained from this source. Such
selected markers may provide the best opportunity to detect stock structure in species with high
dispersal potential and large populations such as Pacific halibut.
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356
Table 1. Staffing and crew aboard longline vessels chartered during winter 2007.
Queen Charlotte Region, F/V Banker II
Name
Position
David Beggs
Vessel Owner and Captain
Darryl Conrad
Mate
Steven Rowlands
Mate
Ivan Loyola
Lead Biologist
Evangeline White
Second Biologist
Dates
February 10-12
February 10-12
February 10-12
February 10-12
February 10-12
Portlock Region, F/V Predator
Name
Position
Don Lane
Vessel Owner and Captain
Clayton Smith
Mate
Sean Rhodes
Mate
Malcolm Milne
Mate
Revelle Russell
Mate
Tom Wilson
Lead Biologist
Tucker Saltau
Second Biologist
Dates
February 1-12
February 1-12
February 1-12
February 1-12
February 1-12
February 1-12
February 1-12
Pribilof Canyon Region, F/V Kema Sue
Name
Position
Jorg Schmeisser
Co-owner and Captain
Peter Freier
Engineer
Stan Van Matre
Mate
Art Gamash
Mate
Bruce Biffard
Lead Biologist
Andy Vatter
Second Biologist
Dates
January 25 - February 12
February 1-12
February 1-12
Aleutian/Andreanof Region, F/V Kema Sue
Name
Position
Norbert Echevario
Co-owner and Captain
Peter Freier
Engineer
Stan Van Matre
Mate
Norbert Adameitz
Mate
Bruce Biffard
Lead Biologist
Andy Vatter
Second Biologist
Dates
February 13 – March 13
357
Table 2. Loci used for routine screening of halibut samples, the reference of original publication,
GenBank accession number, and PCR reaction conditions (MgCl2 concentration, primer
concentration (Primer), annealing temperature (TA), and number of cycles (Cycles)).
Locus
Reference
GenBank
Acc. No
MgCl2
(mM)
Primer
(µM)
TA
(ºC)
Cycles
HhiA44
McGowan et al. 1999
AF133243
2
0.1
55
25
HhiC17
McGowan et al. 1999
AF133244
2
0.2
55
25
Hhi3
Coughlan et al. 2000
AJ270780
1.5
0.2
57
25
Hhi53
AJ270783
1.5
0.2
57
25
Hhi57
AJ270786
2
0.1
55
30
Hhi63
AJ270789
2
0.2
56
25
Hhi58IMB
Reid et al. 2005
AY752692
2
0.2
55
25
Hhi79IMB
Reid et al. 2005
AY752693
2
0.1
55
25
HhiI29*
McGowan et al. 1999
AF133246
1.5
0.2
60
28
Hhi1*
AJ270779
1.75
0.2
60
28
Hhi55*
AJ270784
1.75
0.2
56
30
Hhi55IMB*
Reid et al. 2005
AY752691
1.75
0.1
56
30
Hhi120IMB*
Reid et al. 2005
AY752700
1.5
0.2
56
30
* These loci were screened using M13 primer extensions (Schuelke 2000), and thus also include a 3rd unlabeled
forward primer with the M13 sequence, at a concentration ¼ of the labeled forward M13 primer. These reactions
were done using a touchdown program, with an initial annealing temperature (TA) of 66ºC, a reduction in TA of 2ºC per
cycle, and a final TA given in the table.
358
Table 3. Number of mature halibut sampled each day in each charter region, by size category
(cm fork length) and sex. The dates listed refer to the day upon which sets were hauled, and
the fish sampled.
Queen Charlotte Islands, F/V Banker II
Female
February 11
60-69
0
70-79
2
80-89
11
90-99
18
100-109
17
110-119
20
120-129
9
130-139
13
140+
9
Total
99
Male
February 11
60-69
32
70-79
35
80-89
25
90-99
4
100-109
2
110-119
2
120-129
0
130-139
0
140+
0
Total
100
Portlock Bank, F/V Predator
Female
February 5
February 7
February 8
February 9
February 10
Totals
60-69
0
0
0
0
0
0
70-79
0
0
0
0
0
0
80-89
0
4
1
3
1
9
90-99
3
3
0
1
4
11
100-109
2
4
3
2
3
14
110-119
2
9
0
0
7
18
120-129
2
7
1
0
5
15
130-139
0
8
2
0
7
17
140+
0
5
1
1
9
16
Total
9
40
8
7
36
100
Male
February 5
February 7
February 8
February 9
Totals
59-69
10
0
0
8
18
70-79
11
0
1
26
38
80-89
13
0
0
86
99
90-99
4
0
0
31
35
100-109
0
0
0
8
8
110-119
0
0
0
1
1
120-129
0
0
0
1
1
130-139
0
0
0
0
0
140+
0
0
0
0
0
Total
38
0
1
161
200
Pribilof Canyon, F/V Kema Sue
Female
February 7
February 8
Totals
60-69
0
0
0
70-79
0
0
0
80-89
0
0
0
90-99
0
3
3
100-109
3
21
24
110-119
1
23
24
120-129
2
21
23
130-139
1
16
17
140+
0
9
9
Total
6
94
100
Male
February 7
February 8
Totals
42-69
22
1
23
70-79
18
4
22
80-89
5
11
16
90-99
9
7
16
100-109
6
12
18
110-119
0
3
3
120-129
0
1
1
130-139
0
0
0
140+
0
0
0
Total
60
39
99
Andreanof Islands, F/V Kema Sue
Female
February 23
February 24
February 26
Totals
60-69
0
0
0
0
70-79
0
0
0
0
80-89
0
0
0
0
90-99
0
1
1
2
100-109
1
5
5
11
110-119
1
11
12
24
120-129
1
8
24
33
130-139
0
3
13
16
140+
0
3
11
14
Total
3
31
0
100
Male
February 22
February 23
February 24
February 26
Totals
60-69
0
2
4
1
7
70-79
0
11
7
8
26
80-89
0
25
8
12
45
90-99
2
12
7
11
32
100-109
4
7
6
13
30
110-119
0
2
1
9
12
120-129
0
0
1
2
3
130-139
0
0
0
1
1
140+
0
0
0
2
2
Total
6
59
34
59
158
359
360
HhiI29
N
He
AR
FIS
Hhi55I
N
He
AR
FIS
Hhi55
N
He
AR
FIS
Hhi1
N
He
AR
FIS
Hhi63
N
He
AR
FIS
Hhi57
N
He
AR
FIS
Hhi120
N
He
AR
FIS
48
0.969
16.4
-0.011
30
0.806
7.8
0.049
33
0.975
17.2
0.036
25
0.968
15.9
-0.033
30
0.76
7.2
-0.052
42
0.976
17.2
0.024
***
45
0.94
14.0
0.054
***
27
0.968
16.1
-0.033
41
0.917
12.5
-0.01
43
0.968
16.4
-0.009
***
53
0.913
12.6
-0.033
23
0.854
9.1
-0.019
24
0.839
7.5
0.056
30
0.752
6.0
0.202
35
0.784
7.9
0.052
52
0.661
4.2
-0.019
42
0.646
4.1
0.153
45
0.626
4.2
-0.065
28
0.978
17.5
0.014
RY98F
26
0.978
17.6
0.017
HE98M
31
0.985
18.8
0.017
HE98F
19
0.975
16.6
0.028
26
0.874
11.1
-0.056
23
0.976
17.1
0.02
16
0.74
6.9
-0.183
17
0.862
9.4
-0.092
26
0.699
4.5
-0.045
15
0.983
18.3
-0.017
RY98M
27
0.958
15.0
0.033
36
0.752
7.7
-0.071
*
41
0.969
16.2
0.068
***
47
0.91
12.8
0.065
24
0.851
8.4
-0.028
33
0.98
17.7
0.134
***
39
0.681
4.0
-0.017
PBCF
38
0.975
17.1
-0.026
48
0.921
12.7
-0.04
47
0.972
16.8
0.015
42
0.771
7.3
-0.05
43
0.984
18.4
0.126
***
44
0.629
3.7
-0.265
*
39
0.822
8.2
0.064
PBCM
42
0.974
17.0
0.023
***
47
0.913
12.0
-0.002
*
38
0.971
16.4
0.051
32
0.738
6.6
0.027
19
0.773
6.6
-0.157
29
0.625
4.2
0.062
25
0.979
17.7
-0.021
PTLF
29
0.974
16.8
0.115
42
0.881
11.7
0.081
39
0.978
17.5
0.03
22
0.721
6.9
-0.135
11
0.886
9.0
0.077
26
0.626
3.7
-0.044
15
0.969
15.9
-0.032
PTLM
46
0.967
16.2
0.011
47
0.969
16.2
-0.01
***
47
0.902
11.9
-0.014
39
0.74
6.0
0.064
44
0.968
16.6
0.084
*
47
0.65
4.0
-0.244
**
46
0.813
8.4
-0.016
QCIF
43
0.971
16.3
0.042
43
0.922
12.9
0.016
36
0.736
6.7
0.018
*
43
0.967
15.9
0.038
45
0.825
8.2
0.003
37
0.979
17.7
0.061
*
46
0.667
4.3
-0.076
QCIM
37.2
0.967
16.0
0.010
43.0
0.971
16.6
0.019
***
47.8
0.916
12.7
0.014
33.4
0.748
6.7
0.034
29.6
0.812
7.8
-0.019
42.4
0.649
4.1
-0.057
32.2
0.978
17.7
0.046
AVGF
30.8
0.973
16.6
0.025
40.0
0.903
12.2
-0.002
37.0
0.974
16.9
0.028
29.2
0.755
7.1
-0.060
27.0
0.850
8.8
0.007
36.8
0.653
4.0
-0.055
27.2
0.979
17.6
0.031
AVGM
34.0
0.970
16.3
0.018
40.0
0.972
16.7
0.024
***
43.9
0.909
12.4
0.006
31.3
0.752
6.9
-0.013
28.3
0.831
8.3
-0.006
39.6
0.651
4.1
-0.056
29.7
0.978
17.6
0.038
AVG
Table 4. Microsatellite locus statistics in three samples (HE98 – Portlock Bank 1998; RY98 – Dixon Entrance, Queen Charlotte
Islands 1998; PBC – Pribilof Canyon 2004; PTL – Portlock Bank 2004; QCI – Queen Charlotte Islands 2004, with males (M) and
females (F) treated separately. N: sample size per locus; He: expected heterozygosity; AR: allelic richness adjusted for a minimum
sample size of N=11; FIS value and its significance (*: P<0.05, **: P<0.01; ***: P<0.001). Averages of all females and males (AVGF;
AVGM) and over all samples (AVG), as well over all loci (All) are also shown.
361
HhiC17
N
He
AR
FIS
Hhi53
N
He
AR
FIS
Hhi58
N
He
AR
FIS
Hhi03
N
He
AR
FIS
Hhi79
N
He
AR
FIS
HhiA44
N
He
AR
FIS
All
N
He
AR
FIS
30
0.963
15.6
-0.004
*
35
0.987
19.1
-0.014
39
0.973
17.0
0.025
31
0.974
16.7
0.04
44
0.979
17.7
0.002
38
0.958
15.1
0.039
40
0.945
13.3
0.021
41
0.959
14.9
0.033
34.1
0.918
13.8
0.023
41
0.963
15.6
-0.038
38
0.947
13.7
0.027
44
0.964
15.5
0.057
37.2
0.916
14.0
0.009
42
0.982
18.3
0.03
HE98M
HE98F
Table 4. continued.
44.0
0.909
13.6
0.021
50
0.957
14.8
-0.003
35
0.956
14.7
-0.046
45
0.96
15.1
0.051
52
0.971
16.7
-0.01
51
0.973
16.7
0.073
*
50
0.977
17.5
0.018
RY98F
21.8
0.914
13.7
-0.031
26
0.95
14.5
-0.012
19
0.949
14.8
0.002
21
0.968
15.7
0.016
26
0.969
16.5
-0.032
23
0.972
16.8
-0.028
26
0.964
15.3
0.002
RY98M
40.0
0.915
13.7
0.016
44
0.965
16.1
-0.013
45
0.956
14.6
0
48
0.963
15.5
0.005
42
0.972
16.8
0.02
47
0.975
17.2
-0.026
47
0.967
15.9
0.032
PBCF
45.0
0.912
13.7
-0.013
48
0.96
15.0
0.023
47
0.948
14.3
-0.01
48
0.965
15.7
0.007
48
0.972
16.8
-0.029
*
45
0.966
15.9
0.033
48
0.966
15.9
-0.013
PBCM
45
0.942
13.4
0.104
*
39.5
0.905
13.5
0.018
48
0.962
15.4
0.004
48
0.974
16.8
0.123
***
48
0.97
16.3
-0.009
46
0.978
17.6
0.044
46
0.968
16.1
-0.01
PTLF
33.7
0.909
13.5
0.018
39
0.954
14.2
0.032
44
0.958
15.1
0.003
45
0.966
15.8
-0.012
43
0.959
15.4
0.03
43
0.976
17.1
0.07
40
0.968
16.3
0.018
PTLM
46.2
0.908
13.3
0.002
48
0.963
15.5
0.048
48
0.955
14.4
-0.026
48
0.967
15.9
0.117
*
48
0.96
15.0
0.023
46
0.975
17.2
-0.003
46
0.969
16.1
-0.009
QCIF
42.7
0.912
13.6
0.015
45
0.964
15.5
0.008
45
0.96
14.8
0.028
46
0.957
14.7
-0.022
43
0.959
15.3
0.03
43
0.985
18.8
0.032
40
0.967
15.9
0.017
QCIM
41.4
0.911
13.6
0.013
46.2
0.958
15.1
0.039
42.8
0.955
14.5
-0.008
46.8
0.973
16.8
0.050
***
46.0
0.963
15.5
0.006
46.2
0.977
17.6
0.013
44.2
0.970
16.3
0.025
AVGF
35.4
0.913
13.6
0.003
39.8
0.957
14.8
0.017
39.0
0.952
14.5
0.009
39.6
0.963
15.4
0.006
39.2
0.965
16.0
0.017
38.4
0.978
17.7
0.006
36.8
0.966
15.8
0.004
AVGM
38.4
0.912
13.6
0.008
43.0
0.958
14.9
0.028
40.9
0.954
14.5
0.000
43.0
0.969
16.4
0.034
***
42.8
0.963
15.4
0.006
42.3
0.978
17.6
0.009
40.5
0.968
16.0
0.015
AVG
*
All
samples
RY98M
RY98F
QCIM
QCIF
PTLM
PTLF
PBCM
Locus
Hhi03
Hhi1
Hhi120IMB
Hhi53
Hhi55
*
Hhi55IMB
Hhi57
Hhi58
Hhi63
Hhi79
HhiA44
HhiC17
*
HhiI29
All loci
*** *
PBCF
HE98M
HE98F
Table 5. Results of exact tests for deviations from Hardy-Weinberg equilibrium (HWE).
Fisher’s combinations of probabilities (*: p<0.05, **; p<0.01; ***; p<0.001) over all samples
and over all loci at each site are also provided.
*
*
**
***
*
*
*** ***
*** *
*** *
*
*
*** **
***
*
***
***
Table 6. P values of exact tests (GENEPOP) and permutation tests (FSTAT) for genic
differentiation, as well as P values of FST based permutation tests (GENETIX) at 11 loci and
both sexes combined. Five samples: temporal samples separate; three samples: temporal
samples combined (RYP98+QCI04, HER98+PTL04).
Hhi55I
Hhi55
Hhi1
Hhi63
Hhi57
Hhi120
HhiC17
Hhi53
Hhi03
Hhi79
HhiA44
All Loci
5 samples (98 & 04 sep).
FSTAT GENEPOP GENETIX
0.269
0.238
0.545
0.551
0.346
0.366
0.126
0.132
0.047
0.068
0.088
0.058
0.752
0.715
0.214
0.192
0.984
0.977
0.801
0.835
0.142
0.260
0.156
0.144
0.146
3 samples (98 & 04 comb)
FSTAT GENEPOP GENETIX
0.174
0.127
0.755
0.746
0.045
0.035
0.064
0.089
0.031
0.021
0.084
0.052
0.753
0.809
0.158
0.186
0.923
0.931
0.802
0.819
0.217
0.227
0.048
0.022
0.064
362
Table 7. P values of exact tests (GENEPOP) for pairwise genic differentiation (above diagonal)
and the number of loci (out of 11 loci) showing differentiation (below diagonal) for both sexes
and temporal samples combined (RYP98+QCI04, HER98+PTL04).
PBC
PTL
QCI
PBC
3
2
PTL
0.009
2
QCI
0.077
0.127
363
Pribilof Canyon
Portlock
Bank
Queen
Charlotte
Islands
Andreanof Islands
Figure 1. Collection sites for 2004 and 2007 winter sampling. The Queen Charlotte Islands,
Portlock Bank, and Pribilof Canyon were visited in 2004. The present analysis reports results
of 13 microsatellite loci screened in 96 individuals (48 males and 48 females) collected at each
of these sites, as well as at Portlock Bank and near the Queen Charlotte Islands in 1998-99.
All sites in the figure were sampled in 2007.
364
HER98F
HER98F
PBCF
PTLF
QCIF
RYP98F
HER98M
PBCM
PTLM
QCIM
RYP98M
PBCF
0.0000
PTLF
-0.0009
0.0013
QCIF
0.0009
-0.0001
0.0001
RYP98F
0.0048
0.0035
0.0029
0.0011
HER98M
-0.0009
0.0172
0.0173
0.0160
0.0176
PBCM
-0.0014
-0.0020
0.0168
0.0150
0.0168
-0.0014
PTLM
-0.0020
0.0011
-0.0007
0.0184
0.0215
-0.0002
-0.0021
QCIM
-0.0008
-0.0007
-0.0021
-0.0018
0.0161
-0.0027
-0.0013
-0.0023
RYP98M
0.0001
-0.0017
0.0048
0.0007
0.0027
0.0016
-0.0011
-0.0018
-0.0008
Figure 2. Multidimensional Scaling plot of FST values between all halibut samples, based on 11
loci (r2=0.97, excluding Hhi29, Hhi58). For each site, squares represent females and diamonds
represent males. FST values are provided in the table below the figure.
365
HER98
HER98
PBC
PTL
QCI
RYP98
PBC
0.0002
PTL
0.0019
-0.0008
QCI
0.001
0.0001
0.0007
RYP98
0.0023
-0.0004
-0.0005
0.0001
Figure 3. Multidimensional Scaling plot of FST values at 11 loci. Temporal samples from
Portlock Bank (PTL and HER98) and the Queen Charlotte Islands (QCI and RYP98) cluster
together, while Pribilof Canyon (PBC) is more separated. FST values are shown below the
figure.
366
Oceanographic monitoring on the IPHC setline survey in
2007
Lauri L. Sadorus and Steven R. Hare
Abstract
A Seacat SBE-19 water column profiler was successfully deployed for a seventh year from
a vessel participating in the annual stock assessment survey. Only conductivity, temperature, and
depth profiles were collected in the first four years, and for the past three years, dissolved oxygen
was also measured after a sensor was integrated with the unit. A second profiler, an SBE-19plus,
was purchased this year, which was made possible by a grant from the Oregon Department of
Fish and Wildlife Restoration and Enhancement Program. In total, 168 casts were completed
successfully, encompassing four survey regions.
Introduction
Since the expansion of its survey operations in 1997, the International Pacific Halibut
Commission (IPHC) has annually conducted fishing operations at more than 1000 stations ranging
from Oregon to the Bering Sea. These stations are located on the continental shelf in depths
between 35 and 500 meters, on an equidistant 10-nautical mile grid. As such, the IPHC operates
the largest consistent sampling program of any research agency in the north Pacific. In the late
1990s, the IPHC sought proposals on how this sampling program could be used for other scientific
investigations without affecting the core survey activities. One obvious project was the collection
of oceanographic data. The IPHC already recorded bottom temperature at one-quarter to one-half
of the survey stations; however, the potential existed to sample the entire water column.
To better understand the factors driving fluctuations in growth and recruitment of fish
populations, researchers are paying increasing attention to climatic and oceanic conditions.
Primary and secondary productivity are directly driven by variations in water temperature, salinity,
dissolved oxygen, and other factors. Most of this productivity occurs in the mixed layer, between
20 and 100 meters depth. Acidification of the oceans and upwelling-induced hypoxia are just
two of the phenomenon linked to global climate change in recent years. How these fundamental
changes in the physical and chemical makeup of the ocean waters affect organisms living there
is not well understood. Coupling oceanographic observations with estimates of production from
the IPHC setline survey is an obvious next step to increasing the understanding of what drives the
abundance and distribution of our natural resources.
In 2000, a Seacat SBE-19 water column profiler (Profiler I) was purchased by the IPHC and
deployed aboard a commercial halibut longliner chartered for the annual stock assessment survey.
A pump was added in 2001 to stabilize the salinity profiles. In 2005, a Seabird SBE-43 dissolved
oxygen sensor was added to the unit.
In 2007, the IPHC received a grant from the Oregon Department of Fish and Wildlife
Restoration and Enhancement Program to purchase a Seacat SBE-19plus (an updated version of
the SBE-19 and hereafter referred to as Profiler II) dedicated to the IPHC survey stations off the
Oregon coast. This new profiler was equipped with sensors to measure depth, temperature, salinity,
dissolved oxygen (SBE-43), pH (SBE-18), and chlorophyll (WebLabs ECO-FLRTD).
367
Methods
Profiler I
The original SBE-19 profiler is equipped with an aluminum housing which is rated for depths
to 3400 meters. The SBE-43 dissolved oxygen sensor is equipped with a titanium housing and is
rated for depths to 8000 meters. The unit (without the SBE-43) weighs 9.2 kg in air and 5.2 kg
in water. The profiler is protected by a stainless steel cage, 96 cm tall and specially designed for
this profiler. Software for downloading and displaying the data is provided by the manufacturer.
Communication between the profiler and a computer is accomplished via an RS-232 port.
To adapt the profiler for deployment from a halibut fishing vessel, a system was designed using
weights and floats that permitted the profiler to descend rapidly enough through the water column
to collect valid data, but also ensured that the unit would not crash into or become permanently
attached to the ocean bottom. A sustained descent rate of 1-2 m/sec is generally ideal for CTD
sensors. The weight of the profiler and cage in the water were sufficient that, if the unit was
allowed to freefall, the target descent rate would be achieved.
A 15-meter anchor line was attached to the bottom of the CTD cage using a section of gangion
line as a weak link (in case the anchor could not be freed from the bottom). A 40-pound longline
anchor was attached to the end of the 15-meter line. To the top of the cage, two floats were
attached that effectively offset the weight of the anchor in water. The floats were attached to
standard halibut buoy line which is almost neutrally buoyant.
To deploy the unit, the anchor was lowered into the water followed by the profiler and cage
and then the buoys. After a minimum of 90 seconds in order to acclimate the unit and prime
the pump, the line was released and the full set allowed to freefall. Once the anchor hit the
bottom, the remainder of the unit ceased descending shortly afterward due to the strong positive
buoyancy of the floats compared to the weight of the profiler and cage. During trials with this unit,
recorded bottom depths were compared with profiler measured depth, and it appeared that the unit
descended approximately five meters after the anchor hit bottom and therefore was never in danger
of impacting the bottom. On board the vessel, it was immediately obvious when the anchor hit
bottom because of a noticeable slackening of the line. After the anchor hit bottom, the line was
coiled around the gurdy and the profiler was immediately hauled back.
Once on deck, the conductivity cell was rinsed with a weak solution of industrial cleanser
(Triton X-100), followed by a rinse with distilled water. Tygon tubing was attached to the cell and
filled with a weak bleach solution which remained in place until the next cast.
Profiler II
The SBE-19plus that was purchased in 2007 was deployed fundamentally the same way as
Profiler I with some modifications. A custom bridle assembly and float configuration were devised
to accommodate the added weight of the additional sensors. The pH sensor (SBE-18) had to be
kept moist with a pH 4 solution when not in use and this was accomplished by storing the sensor
with a soaker bottle assembly between casts. The manufacturer suggested field calibrations of the
pH sensor about once a month. This profiler, however, was used for less than one month and so no
calibration was necessary. The WetLabs chlorophyll sensor required only rinsing and then wiping
with a clean cloth.
368
Data capture
Both profilers were equipped with dedicated laptop computers that accompanied them into
the field. Approximately once a day, the profilers were connected to the computers, data were
uploaded, and the profiler units were then reset for the next day’s casts. The data were sent via disk
back to the Seattle office after each trip.
The laptop accompanying Profiler II was newer than that with Profiler I and it was able to run
a more advanced version of the processing software. This gave the field biologist the opportunity
to conduct quality control checks to make sure the unit was performing as expected. The IPHC
plans to purchase a similar computer for Profiler I for the 2008 season.
Results
In 2007, Profiler I was deployed from the F/V Pender Isle and covered three survey regions
(Figs. 1 and 2): Vancouver, Goose Island, and Ketchikan (Soderlund et al. 2008). The first cast was
made on June 5 and the last was made on July 28. A total of 125 profiles were possible and 113
were completed successfully. The unit was not deployed at the remaining stations due to weather
concerns.
Profiler II was deployed off of Oregon at all IPHC Oregon region stations as well as 15
stations that are technically in the Washington grid but positioned off the northern Oregon coast
(Fig. 3). The profiler was deployed from the F/V Bernice for its first trip beginning on June 23, then
was transferred to the F/V Blackhawk which profiled the remaining stations and concluded on July
28. Of a total of 57 stations, 55 were profiled successfully.
Data availability
A primary goal this season was to convert the profiling data into a format that could be linked
to IPHC’s existing database, as well as be available to the public via the IPHC website. Both tasks
are nearing completion and the data are scheduled to be available on the website by the first part of
2008. Additionally, there is an effort underway to submit profiles to the National Oceanographic
Data Center, a NOAA-based oceanographic database that is widely used by scientists around the
world. Spring of 2008 is the projected completion date for this phase of the project. Once both
archiving procedures are established, the current year’s data should become available each summer,
soon after the IPHC field season concludes.
Acknowledgments
We wish to acknowledge the profiling work of the IPHC sea samplers aboard the F/V Pender
Isle, F/V Bernice, and F/V Blackhawk.
References
Soderlund, E., Dykstra, C. L., Geernaert, T., Anderson, E., and Ranta, A. M. 2008. 2007 standardized
stock assessment survey. Int. Pac. Halibut Commission Report of Assessment and Research
Activities 2007. 475-500.
369
130°W
129°W
128°W
127°W
126°W
125°W
2086
52°N
52°N
2072
2085
2084
2083
2079
British Columbia
2082
2081
2080
2077
2076
2075
2074
2071
2070
2069
2068
2067
2066
2064
2063
2062
2061
2060
2059
2058
2057
2056
2055
2054
2053
2052
2051
2043
2050
2049
2048
2047
2046 2042
2041
2045
2044
51°N
2078
2073
2065
51°N
2040
2039
2038
2037
2035
Vancouver Island
50°N
50°N
2034
2033
2032
2031 2030
Legend
49°N
2029
2028 2027
2026
2025 2024 2023
2021 2020 2019
Seacat
49°N
2018 2017 2016
Sets
2015 2014 2013
Successful
2012
2011 2010 2009 2008
Unsuccessful
2007
2006 2005 2004 2003
2002 2001
130°W
129°W
128°W
127°W
126°W
125°W
Figure 1. Stations fished by the F/V Pender Isle in the Vancouver, and Goose Island regions
in 2007. Successful profiler deployments are depicted with a circle. Stations where the vessel
fished but the profiler was either not deployed or unsuccessfully deployed, are depicted with
a x.
370
134°W
133°W
132°W
131°W
Legend
3042
56°N
Seacat
3041
Prince of
Wales
Island
56°N
Sets
3040
Successful
Unsuccessful
3039
3038
3037
3036
3035
3034
3033
3032
3031
3028
3027
3021
3020
55°N
55°N
3030
3029
3026
3025
3024
3023
3019
3018
3017
3016
3007
3006
3005
134°W
3022
3015
3014
3013
3003
3002
133°W
3012
3011
3010
3009
3008
3001
132°W
131°W
Figure 2. Stations fished by the F/V Pender Isle in the Ketchikan region in 2007. Successful
profiler deployments are depicted with a circle. Stations where the vessel fished but the profiler
was either not deployed or unsuccessfully deployed, are depicted with a x.
371
126°W
125°W
124°W
123°W
122°W
121°W
120°W
1058
1057
46°N
46°N
1056 1055 1054
1053 1052 1051
1050 1049 1048
1047 1046 1045
1044 1043 1042
1041 1040
45°N
45°N
1039 1038 1037
1036 1035 1034
1033 1032 1031 1030
1029
1028
Oregon
1027 1026 1025
1024 1023 1022 1021
44°N
44°N
1020 1019 1018
1017 1016
1015 1014
1013 1012
Legend
1011
1010
43°N
Seacat
1009 1008
43°N
Sets
1007 1006
Successful
1005
Unsuccessful
1004
1003
1002
42°N
42°N
1001
126°W
125°W
124°W
123°W
122°W
121°W
120°W
Figure 3. Stations fished by the F/V Berniece and F/V Blackhawk in the Washington, and
Oregon survey regions in 2007. Successful profiler deployments are depicted with a circle.
Stations where the vessel fished but the profiler was either not deployed or unsuccessfully
deployed, are depicted with a x.
372
Estimating halibut hooking success using DIDSON sonar
Stephen M. Kaimmer and Stephen Wischniowski
Abstract
The International Pacific Halibut Commission conducted a fishing experiment using a highfrequency acoustic camera to observe halibut around baited hooks during the summer of 2007.
This study was designed to investigate halibut hooking behaviors to better describe the hooking
success curve for halibut on #3 circle hooks. The data are currently being analyzed.
Introduction
The purpose of the study was to verify, by direct observation, the hooking success curve for
halibut on setlines. Halibut hooking success is an important component of the length-specific
selectivity which is used in the International Pacific Halibut Commission (IPHC) stock assessment
model. This selectivity has most recently been estimated using multiple marking experiments as
being dome shaped: increasing from a low value for small halibut to a peak at some fork length
around 110 to 140 cm, then dropping off again (Clark and Kaimmer 2006). The halibut hooking
success curve was previously estimated from direct camera observations of 42 shallow-water hook
attacks which resulted in 21 halibut captures. This current project was designed to generate a larger
set of observations and operate in deeper, more appropriate depths. The study used a DIDSON
(Dual frequency IDentification SONar) acoustic camera.
Methods
Experimental design
We planned for minimum gear deployment times of one hour, with each deployment observing
four baited hooks. We expected to observe 100 to 200 hook attacks, four times the number of
attacks observed previously with the more conventional underwater camera system. Attack rates
and hooking success were determined for size class of halibut and for halibut overall. Halibut size
was determined using DIDSON techniques demonstrated by Rose et al. (2005). Estimated sizes
were verified by comparison with actual measurements of fish which were hooked and brought to
the vessel on gear retrievals.
Vessel and area
A 10-day experiment was conducted 13-22 August, 2007 from the 17.7-meter fishing vessel
F/V Free to Wander. Fishing locations were based on local knowledge of the vessel crew and a
review of catches at IPHC survey grid stations during the previous three years. IPHC Regulatory
Area 3A was selected as having fishing grounds suitable for the experiment. The vessel was
supplied with a list of IPHC survey stations with high catches of halibut in Area 3A during recent
years.
373
DIDSON camera and frame
Despite conditions of darkness and sometimes high turbidity, the acoustic camera can provide
continuous, high-resolution imagery of approaches to the gear, hook attacks, and escapes. Rose et
al. (2005) first demonstrated the DIDSON acoustic camera as a device for observing fixed fishing
gear and our deployment borrowed much of the design of their system, although our frame was
more rugged (Fig. 1). This system was previously used by the IPHC in 2006 to investigate the
behavior of halibut and rockfish in the vicinity of fish pots (Kaimmer and Wischniowski 2007).
The DIDSON provides multiple, high-resolution images per second across a 29º fan-shaped sector,
with a beam depth of 12º. In high-frequency (1.8 MHz) mode, the 29º sector is acoustically divided
into 96 beams (0.3º each) and the selected range window is divided into 256 equal bins (e.g., 1.6
cm for a 4 m long window). Thus, the pixels at the center of an image with a 4 m range window
are approximately 1.6 cm by 2.6 cm. This resolution is sufficient to show the body shapes of adult
fish, while the update rate of eight frames per second allowed each individual fish to be tracked
through the image. The 12º depth of the acoustic beams limits images to acoustically reflective
objects that pass within a distance equal to 10% of the range above or below that fan shape, while
the view provided is integrated into a single plane. Because better range resolution (limited by 256
range bins) was more important than showing the small wedge of area within a few meters of the
camera, we set the near edge of the image to 3.0 m (Fig. 2). Objects in the resulting null area close
to the camera were not directly imaged, but could produce shadows in the image. The acoustic
camera system used in this study included a hard drive to record the image data. Two 13.2 volt, 9
amp-hr NiMH battery packs in a titanium pressure housing provided the power.
The acoustic camera and the battery case were contained in a cylindrical open frame constructed
of 2½” Schedule 40 aluminum pipe (Fig. 1). Two ELP-362A acoustic pingers manufactured
by BENTHOS1 were attached to the camera cage to assist in gear recovery should the surface
connection become lost.
The camera was mounted so that its viewing angle could be adjusted in the vertical dimension.
The frame itself stood on four 4’ by 2” Schedule 40 pipes. A 20-foot 4½” by 6” aluminum box
beam, made to break down into two pieces for easier transport, was attached across the top of the
cylindrical cage. The other end of the box beam was supported by a 2” Schedule 40 pipe, bent
into a U-shape with a broad, 9-foot middle section and two 4-foot legs. The whole structure was
further strengthened by an 8’ long, 4” box beam laid crosswise near the mid-join, with 2” round
pipes leading from the box beam ends to the end of each leg on the bent support pipe. A triangle
of 5/16” groundline was suspended by shock cords from the legs of the deployment frame at the
end further away from the camera (Figure 1). These cords allowed the groundline to ‘give’ when
a fish was attacking and subsequently darting on the hook. The transducer ‘lens’ of the acoustic
camera was 7 feet away from the nearest end of the groundline triangle, approximately 30” above
the bottom, and oriented horizontally with a downward tilt of ~8º. This distance allowed the entire
setline ‘triangle’ to be inside the acoustic image along with about 3 feet to each side of the gear,
and about 6 feet in front of and beyond the gear. The main beam was above the view of the camera.
A buoyed rope bridle was attached to each end of the main box beam.
The DIDSON is designed to both archive data onto an internalized 8 Gigabyte flashcard, and
output a live NTSC broadcast signal. In order to view the live feed, 1,000 feet of CAT5E twisted
1
Benthos, Inc., 49 Edgerton Drive, North Falmouth, MA 02556 USA.
374
pair, non-shielded Ethernet cable2, reinforced to an 8,000-pound breaking strength, was buoyed
to the surface. This line also served as our deployment and retrieval cable. The live NTSC
signal from the DIDSON was transmitted via the CAT5E twisted pair to a floating, water-tight,
PVC housing. Twisted pair video transmission units (Nitek3 VB31PT video transceiver, and Nitek
TR560 video receiver) on opposite ends of the CAT5E twisted pair cable were used to condition
and boost the signal up to 1200 feet. The NTSC video signal was then broadcast from a 900 MHz
FM micro audio/video transmitter (AVX-900-T4) capable of a range of one mile. The signal was
received by a directional Yagi-900 super high gain receiver antenna, and interpreted by an AVX
900 receiver. The live video output was then viewed on a Planar 14-inch color video monitor and
recorded on a Sony (GV D1000E) digital VCR.
On the third day, we lost the transmission functions of this cable, and subsequent deployment
and retrievals were made using a 1,200 foot length of 9/16” American4 Ultra-blue line, which was
then buoyed to the surface.
Data collection and archiving
The DIDSON stores files of the sonar data on its onboard flashcard. After each deployment,
these files were uploaded to a laptop and also backed up on an external hard drive, giving two file
copies. The original files were then erased from the DIDSON.
Gear setting and hauling information was entered on standard IPHC data forms. The captain
completed a Captain’s Set Form. In addition, a unique Set Form A was created to include information
specific to the DIDSON deployments.
Results
Fishing locations and fish catches
Actual fishing locations are given in Table 1 and shown in Figures 3 and 4. The vessel deployed
the apparatus 68 times in total. Deployments, which averaged about one hour in duration, were
made between the hours of 6 AM and 10 PM. As many as twelve deployments were made per
day.
The first three deployments were conducted in shallow water from the anchored vessel in
order to configure the DIDSON and frame. The next five days were spent in Prince William
Sound, around Montague Island. Catches on these days were disappointing. For the remainder
of the charter, we ran to outside waters around Portlock Bank where catches were more favorable.
As many as four halibut were caught on many of these deployments. The charter ended a day
early to avoid a large weather system. Because of a perceived problem with the DIDSON battery
case, combined with the almost 14-hour run from the fishing area to harbor, it was decided that it
would not be practical to return for a single, final day’s fishing. In all, we caught 50 halibut on the
DIDSON gear.
While the live video feed remained in operation, we took note of halibut behaviors at sea. For
each gear deployment, first observations and subsequent behaviors of halibut were observed and
recorded. These behaviors were classed into one of the following categories: 1) approach or first
2
3
Purchased from Falmat Custom Cable Technologies, 1873 Diamond Street, San Marcos, CA 92069
Nitek, 5410 Newport Dr. Ste 24, Rolling Meadows, IL 60008-3722
375
observation; 2) lying on the seafloor; 3) biting the hook; 4) darting while hooked; and 5) successful
escape. Subsequent to the loss of the transmission capability of our hauling cable, we performed
cursory video file reviews after each download. Final file review will be conducted during the
winter of 2007 and into 2008.
Discussion
This project had many successes, not the least of which were the excellent performance of the
DIDSON sonar and the deployment frame and protocol, and the continuing development of the
data transmission system. It is unfortunate that we did not observe more fish captures. We hope
to have enough observations of hook attacks and hooking events to generate an initial estimation
of the hooking success curve. We have proposed a subsequent trip to be conducted during 2008
which will gather more observations on the #3 hooks, as well as a fresh set of observations on the
smaller #6 hooks.
References
Clark, W. G. and Kaimmer, S. M. 2006. Estimates of commercial longline selectivity for Pacific
halibut (Hippoglossus stenolepis) from multiple marking experiments. Fish. Bull. 104465467.
Kaimmer, S. M. and Wishniowski, S. 2007. Examining the behavior of rockfish and halibut around
pots. Int. Pac. Halibut Comm. Report of Assessment and Research Activities 2006:239-249.
Rose, C. S., Stoner, A. W., and K. Matteson, K. 2005. Use of high-frequency imaging sonar to
observe fish behaviour near baited fishing gear. Fish Res. 76 (2):291-304.
376
Table 1. Fishing locations during the 2007 DIDSON hook study.
Set
Number
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
Date
13-Aug
13-Aug
13-Aug
14-Aug
14-Aug
14-Aug
14-Aug
14-Aug
14-Aug
15-Aug
15-Aug
15-Aug
15-Aug
15-Aug
15-Aug
15-Aug
16-Aug
16-Aug
16-Aug
16-Aug
16-Aug
16-Aug
16-Aug
16-Aug
17-Aug
17-Aug
17-Aug
17-Aug
17-Aug
17-Aug
17-Aug
17-Aug
17-Aug
18-Aug
18-Aug
18-Aug
18-Aug
18-Aug
18-Aug
18-Aug
18-Aug
18-Aug
20-Aug
20-Aug
20-Aug
20-Aug
Latitude
59º56.71’
59º 56.71’
59º 56.71’
60º 05.03’
60º 05.03’
60º 05.03’
60º 04.04’
60º 04.04’
60º 04.04’
60º 09.46’
60º 04.32’
60º 04.55’
60º 04.21’
60º 04.21’
60º 04.21’
60º 04.21’
60º 04.08’
60º 04.37’
60º 04.06’
60º 08.27’
60º 08.26’
60º 08.26’
60º 05.03’
60º 05.06’
60º 05.05’
60º 05.12’
60º 05.04’
60º 04.97’
60º 06.26’
60º 04.17’
60º 04.92’
60º 05.59’
60º 05.76’
60º 20.02’
60º 19.97’
60º 20.03’
60º 20.34’
60º 09.91’
60º 04.66’
60º 04.66’
60º 04.66’
60º 04.66’
59º 00.79’
59º 00.61’
58º 50.10’
50º 50.20’
Longitude
148º 12.10’
148º 12.10’
148º 12.10’
147º 38.30’
147º 38.30’
147º 38.30’
147º 39.90’
147º 39.90’
147º 39.90’
147º 34.30’
147º 39.60’
147º 39.50’
147º 39.70’
147º 39.70’
147º 39.70’
147º 39.70’
147º 40.00’
147º 40.00’
147º 40.10’
147º 35.60’
147º 35.70’
147º 36.10’
147º 38.20’
147º 38.20’
147º 38.40’
147º 38.40’
147º 38.30’
147º 38.30’
147º 38.00’
147º 39.90’
147º 39.40’
147º 37.70’
147º 37.70’
147º 30.90’
147º 30.40’
147º 29.70’
147º 27.90’
147º 30.90’
147º 35.90’
147º 35.20’
147º 35.20’
147º 35.20’
148º 13.80’
148º 13.90’
148º 15.00’
148º 15.10’
Depth
(fm)
19
19
19
31
31
31
54
54
54
46
56
53
48
48
48
48
51
50
59
40
35
66
38
38
33
45
32
33
33
52
49
41
31
79
65
53
18
28
68
58
58
58
95
100
151
150
Halibut
catch
(no.)
0
0
0
0
0
0
1
2
1
0
1
0
1
1
1
2
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
Comments
Gear calibration, vessel at anchor
Prince William Sound, west of Montague
Portlock bank
Portlock bank
Portlock bank
Portlock bank
Portlock bank
377
Table 1. continued.
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
21-Aug
21-Aug
21-Aug
21-Aug
21-Aug
21-Aug
21-Aug
21-Aug
21-Aug
21-Aug
22-Aug
21-Aug
22-Aug
22-Aug
22-Aug
22-Aug
22-Aug
22-Aug
17-Aug
17-Aug
22-Aug
22-Aug
58º 29.21’
58º 29.16’
58º 29.04’
58º 29.38’
58º 29.80’
58º 29.72’
58º 29.67’
58º 29.61’
58º 30.42’
58º 30.20’
58º 29.92’
58º 30.08’
58º 30.10’
58º 30.10’
58º 30.02’
58º 30.00’
58º 30.01’
58º 30.06’
58º 30.04’
58º 30.14’
58º 29.97’
58º 30.09’
148º 34.50’
148º 34.80’
148º 34.90’
148º 34.30’
148º 33.80’
148º 33.80’
148º 33.80’
148º 33.80’
148º 34.00’
148º 33.90’
148º 53.00’
148º 53.00’
148º 53.00’
148º 53.00’
148º 52.50’
148º 52.80’
148º 53.10’
148º 53.10’
148º 53.10’
148º 53.00’
148º 53.00’
148º 53.00’
72
72
71
73
74
75
75
75
73
73
62
62
62
62
62
62
62
62
63
63
63
63
4
2
3
1
1
1
1
2
2
1
3
1
1
4
0
0
2
2
2
2
2
1
378
Portlock bank
Portlock bank
Portlock bank
Portlock bank
Portlock bank
Portlock bank
Portlock bank
Portlock bank
Portlock bank
Portlock bank
Portlock bank
Portlock bank
Portlock bank
Portlock bank
Portlock bank
Portlock bank
Portlock bank
Portlock bank
Portlock bank
Portlock bank
Portlock bank
Portlock bank
Figure 1. Deployment frame for using the DIDSON acoustic camera to observe fish behavior
around baited hooks.
379
Figure 2. A DIDSON image showing range markers (in meters), groundline, rocks, shadows
from rocks, halibut, halibut ‘shadow’, and other small fish. The ring at the bottom right shows
vertical and horizontal orientation, and compass orientation.
380
158°0'W
156°0'W
61°0'N
154°0'W
152°0'W
150°0'W
148°0'W
#
###
Sets 173-176
146°0'W
Prince William Sound
61°0'N
##
##
#
#
#
#
#
##
#
Sets 143-172, 177-181 #
#
#####
#
#
60°0'N
Inset Area
#
140
141
142
59°0'N
#
60°0'N
#
Sets 140-142
59°0'N
#
#
# #
58°0'N
58°0'N
Kodiak Island
57°0'N
57°0'N
158°0'W
156°0'W
154°0'W
152°0'W
150°0'W
148°0'W
146°0'W
Figure 3. Station positions near Prince William Sound during the 2007 DIDSON hook
study.
381
158°0'W
156°0'W
154°0'W
61°0'N
152°0'W
150°0'W
148°0'W
146°0'W
Prince William Sound
#
61°0'N
Sets 182, 183
##
#
##
#
#
#
#
#
Sets 184, 185
60°0'N
#
60°0'N
#
59°0'N
Inset Area
#
#
#
#
#
#
59°0'N
Sets 196-207
Sets 186-195
#
#
# #
58°0'N
58°0'N
Kodiak Island
57°0'N
57°0'N
158°0'W
156°0'W
154°0'W
152°0'W
150°0'W
148°0'W
Figure 4. Station positions near Portlock Bank during the 2007 DIDSON hook study.
382
146°0'W
2007 hook size and spacing experiment
Stephen M. Kaimmer and Bruce M. Leaman
Abstract
The International Pacific Halibut Commission (IPHC) conducted a fishing experiment using
different combinations of hook sizes and hook spacings during the summer of 2007. The 2007
experiment was a repeat of an experiment conducted in 2005, that was conducted in an area
with higher halibut densities. This study was designed to address potential differences in CPUE
and size selectivity of selected combinations of hook size and hook spacing in the commercial
fishery relative to the configuration of the standard IPHC survey skate. Compared with the 2005
experiment, the 2007 experiment in lower halibut density grounds resulted in a strong relationship
between hook spacing and the weight of legal-sized halibut caught. Larger hook spacing resulted
in higher catches of legal-sized halibut, by weight. Hook size had negligible impact on catch of
legal fish (weight or number) but smaller hooks caught more sublegal-sized fish.
Introduction
The International Pacific Halibut Commission (IPHC) conducted a fishing experiment using
different combinations of hook sizes and hook spacings during the summer of 2007. This study
was a companion to one conducted in 2005. Both studies were designed to address potential
differences in CPUE and size selectivity of selected combinations of hook size and hook spacing
in the commercial fishery, relative to the configuration of the standard IPHC survey gear skates of
100 #31 circle hooks, with 18-foot spacing.
The adoption of Individual Quota management for halibut and sablefish, together with
coincident seasons for these species, has resulted in an increased amount of mixed-target or
combination fishing for both halibut and sablefish in Alaska. The optimum gear for the two species
is quite different, with sablefish gear using smaller #5 or #6 hooks and short 36-48” spacing, while
optimum gear for halibut may be larger #3 hooks with 15-18’ spacing. IPHC assessments make
corrections for hook spacing relative to the IPHC standard 1800-ft, 100-hook skate. However, the
adjustment is based on a relationship developed in the 1970s from spacing experiments using Jhooks. No adjustment of CPUE for hook size is made. There is concern that smaller hooks may
affect size selectivity and, hence, CPUE. The increased use of combination gear for sablefish and
halibut fishing within the commercial fishery has prompted our investigation of the relationship of
catching power by these different gear types. The 2005 study was conducted in IPHC Area 3A,
where halibut densities are relatively high, and was reported on in the 2005 RARA (Leaman and
Kaimmer 2006). The 2007 study was conducted in the relatively lower-density IPHC Area 2C.
For clarity in our gear codes for this project, used the 3, 4, 5, 6 numbering scheme for hook sizes. This nomenclature
corresponds to the 16, 15, 14, 13 scheme, in that the large #3 hook is equivalent to a 16/0 hook, the smaller #4 is
equivalent to 15/0, and etc
1
383
Experimental design
The 18.3-meter F/V Proud Venture was chartered to conduct the hook size and spacing
experiment in IPHC Regulatory Area 2C (southeastern Alaska). We initially bid this project to be
conducted in Area 2B (British Columbia), but regulatory difficulties which would have prevented
fish sales from this experiment forced us to make a last minute venue change to Alaskan waters.
The experimental design was the same as that used in 2005, and required the successful hauling
of 44 strings of gear. Fishing locations were based around IPHC setline survey grid stations in
the southern regions of Area 2C. The vessel was supplied with a suggested list of fifty fishing
locations whose survey CPUE had averaged in the top 40-85 percent in IPHC Area 2C in the 20042006 three-year period.
The experiment was a randomized block design with two factors: hook size and hook spacing.
The four levels of hook size were #3 - #6 hooks (alternate designations are hook sizes 16/0 – 13/0).
The four spacing levels were 18, 12, 9, and 3.5 feet. Not all combinations of hook size and spacing
were fished. While all these hook sizes and spacings are present to some extent in the commercial
fishery, almost none of the large-hook gear is fished on short spacings, and likewise almost none of
the small hooks are fished on long spacings. The combinations tested in the experiment are shown
below.
Hook Size
Hook
Spacing
3.5 ft
9 ft
12 ft
18 ft
#6
X
X
X
#5
X
X
X
#4
#3
X
X
X
X
X
X
For clarity, we standardized our hook size nomenclature so that hook sizes were termed as
sizes #3, #4, #5, and #6. Our hook spacings were recorded as two-digit integers, so, as examples,
the 3.5 foot spacing was recorded as 04 and the 9 foot as 09. Using this nomenclature, the gear
code was expressed as a three-digit integer: the first digit giving the hook size, and the second and
third, the hook spacing. Thus, the skate with #4 hooks at a 12-foot spacing was given the code
“412”, #3 hooks at 18-foot were coded as “318”, and so on, as shown below.
Hook Size
Hook
Spacing
3.5 ft
9 ft
12 ft
18 ft
#6
604
609
612
#5
504
509
512
#4
#3
409
412
418
309
312
318
For each day’s fishing, two strings of twelve 100-hook skates were set, with the hook and
spacing factors randomized by skate within each string. The order of the skates in each set was
determined by reference to a random setting order table. Twelve skates of each gear were included
in each string, representing one each of the twelve hook size and spacing combinations as shown in
the above table. The sample size for the experiment was based on an analysis of 2003 survey data
384
for Areas 3A and 3B. With an α = 0.05 and power of 0.90, we needed a sample size of 480 skates
(forty 12-skate sets) to have a minimum detectable difference = 60 lb/skate. Our bid specifications
for the experiment called for 22 stations (44 sets).
Note that the skates were a standard number of hooks rather than a standard length. Therefore,
the length of the skates varied from 1800 ft (100 hooks at 18 ft spacing) to 350 ft (100 hooks at 3.5
ft spacing). The length of each string was approximately 12,700 feet, about equivalent in length
to seven standard IPHC survey skates (1800-foot each). Hook size, spacing, and gangion type and
length were constant within a skate, i.e., each of the 12 skates was a unique combination of hook
size and spacing, with standard 24-inch, 60-thread count, hard-lay gangions (after tying) on all
gear. The vessel was responsible for construction of the gear and for rigorous gear maintenance
before each resetting of the gear. Hook counts were conducted on all gear prior to setting to ensure
adherence to the 100-hook per skate specification. Damaged or missing hooks or gangions were
replaced prior to setting.
All strings were set in parallel berthings, greater than one and less than three nautical miles
apart, in a similar depth stratum. Two 12-skate sets (24 skates total) were made per day and
were treated as a single station. Station positions were occupied progressively to avoid depletion
issues.
Measured characteristics for halibut were length on all fish, sex, and maturity on all legal-sized
(≥ 82 cm) fish, and a 10% random sample of sex and maturity of sublegal-sized fish. Otoliths for
age determination were not collected. All station and fishing data standard to assessment survey
fishing were also collected.
Setting began at approximately 5:00 AM local time or at first light each morning. When all
strings were set, the vessel returned to the first string and began hauling after the set had been
soaking at least five hours. During hauling, all halibut were brought aboard. Sublegal-sized
fish which were not part of the 10% random sample were measured and returned to the water
unharmed. All legal-sized halibut and some bycatch (Pacific cod and rockfish) caught on all skates
were retained and sold to offset charter costs.
The chartered vessel was responsible for completing all experimental sets in the experiment
effectively. Sets were considered effective if the vessel properly set the gear and hauled back
within 24 hours. Situations resulting in the data from a set being deemed ineffective for the
experiment and requiring re-setting of the string included loss of function of ≥ 33% of the total
number of hooks for a string. Loss of function could be the result of lost gear, snarls, shark or
mammal predation, or excessive sand flea activity. No sets were deemed ineffective during either
the 2005 or the 2007 experiment.
The fishing gear was provided as half skates coiled in tubs. During setting, a weight of
approximately 5 to 10 pounds was snapped on the groundline at each skate junction. A color
coding system was devised to mark each skate end using colored twine to represent both the hook
spacing and hook size on that gear. This coding was combined with a series of plasticized charts
which specified, with both colors and text, the randomized order for the day’s fishing. All gear was
hand baited with the same bait used in standard IPHC grid charters: frozen chum salmon, number
2 semi-bright, or better. The crew was responsible for cutting the salmon into pieces sized between
1/4 and 1/3 pound for baiting the gear. Bait cutting was monitored by IPHC staff to ensure the bait
size was consistent across all gear types.
This experiment had a number of features which required special data handling. The most
obvious was the use of 12 skates in each set (our data archives only allow up to ten skates per
385
set), and the recording of depth and location for each skate. Our data archive format only allows
up to ten skates per set. This restriction was accommodated by creating a unique data form with
room for 12 skates. Less obvious, but as demanding, was the fact that each skate was unique. For
each skate, we needed to keep track of hook counts; the hook size and spacing; and whether that
particular skate was effective for the experiment, and if not, why. We handled these data needs
by designing special versions of the Captain’s Set Form and Set Forms A and B used normally
on IPHC assessment surveys and by some special protocols during data entry and subsequent
retrievals. Using codes developed for this experiment, we were then able to record hook sizes and
spacings, hook counts, and depth for each skate set.
We changed the ineffective set criterion so that it could be applied to individual skates. The
criterion for an ineffective skate was if 33% or more of the hooks in that skate were compromised,
rather than 33% by set as is used on standard IPHC surveys. If more than 33% of the skates in a
set were deemed ineffective, the string would have to be reset.
Results
Fishing commenced on 14 July and was completed on 12 August. The experiment was
completed with three 6-fishing day trips, and one 5-fishing day trip. A total of 44 sets were
successfully completed, occupying 22 station locations (Table 1 and Figures 1 and 2). During the
course of the experiment, the gear caught 3,325 legal-sized halibut (this compares to 10,408 legalsized halibut caught during the 2005 experiment), with an estimated weight of 85,421 net pounds,
and 2,596 sublegal-sized halibut. Fishing depth ranged from 29 to 160 fathoms.
Table 2 presents a preliminary summary of the results by hook size and hook spacing. These
are simple tabulations. The CPUE of legal-sized halibut increased with increasing hook spacing,
and generally increased with hook size. The CPUE of the largest hooks (#3) was actually less than
the next smaller hooks (#4). There is no clear relationship between the catch of sublegals and hook
spacing, although sublegal catch is higher on the smaller hooks.
A complete analysis of the results of this experiment, in combination with the 2005 experiment,
is in progress.
References
Leaman, B. M. and Kaimmer, S. M. 2006. 2005 hook size and spacing experiment. IPHC Report
of Assessment and Research Activities 2005: 215-231.
386
Table 1. Fishing locations and halibut catches during the 2007 Gear Effect experiment.
Set
Number
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
Date
14-Jul
14-Jul
15-Jul
15-Jul
16-Jul
16-Jul
17-Jul
17-Jul
18-Jul
18-Jul
22-Jul
22-Jul
23-Jul
23-Jul
24-Jul
24-Jul
25-Jul
25-Jul
26-Jul
26-Jul
27-Jul
27-Jul
30-Jul
30-Jul
31-Jul
31-Jul
1-Aug
1-Aug
2-Aug
2-Aug
3-Aug
3-Aug
7-Aug
7-Aug
8-Aug
8-Aug
9-Aug
9-Aug
10-Aug
10-Aug
11-Aug
11-Aug
12-Aug
12-Aug
Depth (fm)
Minimum Maximum
108
129
109
160
40
65
49
80
99
105
110
121
112
114
110
110
126
143
129
137
107
108
112
114
71
77
70
76
66
73
64
93
40
49
41
68
30
46
29
55
52
66
54
58
113
114
98
99
99
103
89
94
77
84
91
97
101
107
97
106
98
103
99
103
43
64
42
67
71
77
82
90
68
73
72
75
88
92
76
80
77
90
84
87
67
73
66
70
North
latitude
56°00.10
56°00.91
56°30.41
56°29.25
55°50.53
55°50.42
55°58.44
55°57.47
56°40.49
56°40.06
56°20.77
56°19.25
56°19.58
56°19.72
56°08.60
56°11.23
56°18.61
56°20.84
56°00.23
55°58.84
56°29.39
56°29.32
57°09.48
57°10.47
56°09.88
56°12.64
56°10.50
56°10.03
56°09.80
56°10.82
56°14.00
56°14.09
54°59.63
55°00.12
54°50.03
54°48.28
54°51.40
54°52.17
54°48.04
54°49.92
54°59.02
55°01.24
54°51.94
54°52.97
West
longitude
132°31.18
132°32.53
133°44.97
133°44.44
135°10.02
135°13.01
135°13.04
135°13.64
135°53.55
135°50.67
135°31.11
135°31.91
134°56.66
134°59.08
134°19.96
134°19.92
134°18.94
134°19.15
134°19.55
134°22.24
135°13.98
135°16.59
136°11.36
136°07.22
134°55.66
134°56.69
134°47.36
134°52.05
134°56.89
135°00.27
135°14.77
135°11.03
133°27.11
133°28.86
133°43.59
133°43.30
133°44.06
133°47.89
133°47.20
133°47.58
134°01.68
134°04.30
133°44.96
133°45.06
Pounds
≥ 82 cm
690.7
801.2
237.5
714.6
1989.4
1139.1
1339.4
1647.9
712.1
313.7
748.6
353.3
183.7
624.1
475.3
703.3
697.1
424.6
470.0
253.6
592.8
816.9
673.0
565.2
1947.4
901.4
772.8
1112.7
764.0
739.7
868.5
596.3
759.5
596.3
2387.7
1791.6
2593.1
2113.0
771.1
2169.3
446.9
547.1
897.9
1015.5
Number
< 82 cm
9
17
7
4
92
25
53
68
9
7
14
15
35
45
27
11
35
17
26
17
22
37
18
24
80
25
19
31
19
28
15
14
147
176
10
19
14
16
6
10
0
0
20
20
387
Table 2. Summary statistics of catch rates (net lb/100 hooks and net count/100 hooks) on
experimental skates as a function of hook spacing and hook size from the 2007 Gear Effect
experiment.
Hook spacing (ft)
N
Mean legal weight
Std.dev. of legal weight
Mean sublegal count
Std. dev. Of sublegal count
3.5
88
130.7
126.4
4.4
6.8
N
Mean legal weight
Std.dev. of legal weight
Mean sublegal count
Std. dev. Of sublegal count
#6
132
145.2
128.5
6.3
8.0
9
176
149.4
114.3
4.8
5.9
Hook Size
#5
132
152.8
144.6
4.6
6.1
388
12
176
173.3
150.8
5.3
6.5
18
88
194.6
157.8
4.7
5.3
#4
132
179.7
139.1
4.3
4.8
#3
132
169.4
138.6
4.3
5.1
136°0'W
135°0'W
134°0'W
133°0'W
AK
109
110
Baranof Island
57°0'N
57°0'N
BC
96
Map Area
95
56°30'N
89
107
108
56°30'N
90
98
104
100
97
103
99
117
118
116
115
112
111
114
102
101
106
56°0'N
93
92
94
88
105
56°0'N
91
Prince of Wales Island
136°0'W
135°0'W
134°0'W
133°0'W
Figure 1. Northern fishing locations with set numbers for the 2007 IPHC Gear Effect
experiment.
389
135°0'W
134°0'W
133°0'W
55°30'N
55°30'N
113
Prince of Wales Island
128
55°0'N
120
127
124
126
125
AK
130
129
123
121
122
55°0'N
119
Forrester Island
BC
54°30'N
87
54°30'N
Map Area
135°0'W
134°0'W
133°0'W
Figure 2. Southern fishing locations with set numbers for the 2007 IPHC Gear Effect
experiment.
390
2007 dogfish mischmetal experiments
Steve Kaimmer
Alan Stoner
Fisheries Behavioral Ecology Program, NOAA
Abstract
Recently, rare earth metals have been shown to have deterrent effects on members of the shark
family. These effects are the result of electric fields created by these metals in seawater, which are
sensed and avoided by sharks. The IPHC conducted two experiments during 2007 to see whether
these deterrent effects might help keep dogfish off halibut longlines. Two studies, one in the
lab and one in the field, showed positive deterrent effects of rare earth mischmetals on the spiny
dogfish. The application does not appear to be a practical technique at this time for the Pacific
halibut fishery.
Introduction
During 2007, the International Pacific Halibut Commission (IPHC) and the Fisheries Behavioral
Ecology Program of the National Marine Fisheries Service Alaska Fisheries Science Center in
Newport, Oregon, conducted joint studies on the effects of rare earth metals on dogfish and halibut
feeding behavior. These studies were jointly funded by the IPHC and the National Oceanographic
and Atmospheric Administration’s Bycatch Reduction Program. The study purpose was to
investigate the potential for using these metals as a deterrent for spiny dogfish (Squalus acanthias)
capture on halibut longlines. There were two components to the study in 2007. The first was a
laboratory study where attacks on baits by both dogfish and halibut were tested in the presence
of two different rare-earth materials (neodymium-iron-boride magnets and cerium mischmetal1)
believed to deter elasmobranch catch. Experiments were conducted with spiny dogfish and with
Pacific halibut (Hippoglossus stenolepis) in pairwise tests of the rare-earth materials with inert
metal decoys. Results of these experiments showed promise for the mischmetal, and are reported
in Stoner and Kaimmer (in review). Encouraged by the results of the laboratory studies, a fishing
experiment, the second component of this study, was then conducted in August of 2007 using
pieces of the mischmetal attached to circle hooks to determine whether the deterrent effect seen in
the laboratory would transfer to the field.
Experimental design
The 18.3-meter F/V Predator was chartered to conduct the field mischmetal experiment in
IPHC Regulatory Area 3A. The experimental design required the successful hauling of 36 strings
of gear. Fishing locations were chosen based on the local knowledge of the vessel captain.
1
a cerium-rich mixture of lanthanide (rare earth) metals
391
The experiment was a randomized block design, with two treatments and one control (Table
1). The first treatment had a triangular piece of mischmetal, 4.5 cm on a side and about 0.7 cm
thick, weighing about 50 grams, attached to the hook (Fig. 1). The second ‘dummy’ treatment had
a triangular piece of steel of the same size, with a weight of about 55 grams, similarly attached.
These were compared with hooks with no attached metal. The fishing gear otherwise met our
survey criteria: #3 hooks fixed to groundline at 18-foot intervals. Each set was comprised of three
50-hook skates, one skate of each treatment, randomly arranged into each set of gear. Gear was
set at approximately 0800 local time or first light, hauled after a minimum two-hour soak time,
and then reset and re-hauled (with a two-hour soak) through the day. The most gear set in any one
day was seven sets.
The vessel was responsible for construction of the gear and for rigorous gear maintenance
before each resetting of the gear. Hook counts were conducted on all gear prior to setting to ensure
adherence to the 50-hook per skate specification. Damaged or missing hooks or gangions were
replaced prior to setting. Data collected included length for all halibut, and counts and sample
weights for all other catches. During hauling, all halibut were brought aboard. Sublegal-sized
fish were measured and returned to the water unharmed. All legal-sized halibut and some bycatch
(Pacific cod, Gadus macrocephalus) were retained and sold to offset charter costs.
The fishing gear was provided as 50-hook skates coiled in tubs. Because of the weight of the
mischmetal and dummy metal pieces, weights were not added to the gear during setting. A color
coding system was devised to mark each skate end with colored twine to represent the treatment
on that skate. This coding was combined with a series of plasticized charts which specified, with
both colors and text, the randomized order for the day’s fishing. All gear was hand baited with the
same bait used in standard IPHC grid charters: frozen chum salmon (Oncorhynchus keta), number
2 semi-bright or better. The crew was responsible for cutting the salmon into pieces sized between
1/4 and 1/3 pound for baiting the gear. Care was taken to keep the bait size consistent across all
gear types. Research staff monitored bait size during the charter to ensure compliance to charter
standards.
Field fishing results
Fishing commenced on 25 September and was completed on 1 October. A total of 36 sets were
successfully completed, with all fishing conducted within Kachemak Bay, and within 10 miles of
the Homer Spit (Table 2 and Fig. 2). Halfway through the experiment, the mischmetal pieces were
removed from the hooks and weighed. The mischmetal reacts electrochemically with seawater,
giving off an electrical field while undergoing a process of ionization and dissolution, much like a
protective zinc anode, but at a much faster rate. On average, the mischmetal triangles had lost half
their mass during the first three days of fishing, about 20 hours of soak time on average for each
piece of metal. Fresh pieces of metal were put on for the second half of the experiment.
During the course of the experiment, the gear caught 141 legal-sized halibut, with an estimated
weight of 2,800 pounds; 178 sublegal-sized halibut; and 2,062 dogfish (Table 3). Fishing depth
ranged from 29 to 58 fathoms. The mischmetal gear caught fewer dogfish on average for 50
hooks fished (17.0) compared to the dummy and standard gear (19.2 and 21.1, respectively). The
mischmetal gear caught slightly more halibut on average for 50 hooks fished (27.0) compared to
the dummy and standard gear (26.5 and 24.6, respectively).
392
We analyzed the data using an analysis of variance (ANOVA) with block (set) and treatment
effects. It was not necessary to transform the data prior to analyses, as the ANOVA assumptions
of normality and constant residual variance were reasonable. There was very strong evidence for
differences among the three treatments (F(2,70)=11.9, p<0.0001, Table 4). Pairwise comparisons
of the three treatment means were done using Tukey’s HSD method. The mischmetal treatment
‘M’ had a significantly lower mean dogfish catch than both treatments C and D (p<0.0001 and
p=0.029 respectively), while there was little evidence for a difference between treatments C and D
(p=0.069). Although we did not perform a statistical analysis, the mischmetal gear also caught far
fewer skates, another elasmobranch species.
An ANOVA on halibut catch weights showed no significant difference among the three
treatments (F(2,70)=0.06,p=0.9439).
Discussion
The field trials showed a significant, 20 percent, decrease in the dogfish catches on gear
protected with mischmetal. While this was statistically significant, the practical application of
this particular metal for dogfish catch reduction is unlikely. The metal itself was reasonably
expensive, somewhat difficult to work with metallurgically, and had a high rate of dissolution.
There may be other reactive metals, or electrical field generators, which would be practical. The
difference in effectiveness from the lab to the field might be due to a ‘frenzy’ type of feeding
behavior. What might deter a single dogfish in a lab setting becomes less of a barrier when many
dogfish are approaching baits in the field.
References
Stoner, A. W. and Kaimmer, S. M. (in review). Reducing elasmobranch bycatch on longline gear:
laboratory investigation of rare earth metal and magnetic deterrents with spiny dogfish and
Pacific halibut.
393
Table 1. Gear configurations used in the 2007 Dogfish mischmetal experiment.
Gear
Standard
Mischmetal
Dummy
Code
C
M
D
Description
#3 hook
#3 hook with attached mischmetal triangle
#3 hook with attached dummy metal
Table 2. Fishing locations during the 2007 Dogfish mischmetal experiment.
Set
Number
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
Date
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Sep-07
Oct-07
Oct-07
N. latitude
59º 39.68’
59º 40.24’
59º 40.50’
59º 39.75’
59º 39.21’
59º 39.64’
59º 40.00’
59º 35.20’
59º 37.28’
59º 39.73’
59º 38.39’
59º 37.00’
59º 38.48’
59º 37.33’
59º 35.75’
59º 36.91’
59º 36.95’
59º 37.00’
59º 36.66’
59º 37.55’
59º 30.91’
59º 29.67’
59º 30.32’
59º 30.62’
59º 30.49’
59º 29.74’
59º 30.30’
59º 29.55’
59º 29.51’
59º 30.70’
59º 31.59’
59º 31.91’
59º 32.38’
59º 32.38’
59º 37.06’
59º 37.95’
W. Longitude
151º 11.85’
151º 10.92’
151º 11.71’
151º 12.20’
151º 12.75’
151º 13.12’
151º 11.72’
151º 17.81’
151º 14.29’
151º 12.34’
151º 17.66’
151º 17.38’
151º 15.56’
151º 14.59’
151º 18.41’
151º 14.56’
151º 12.13’
151º 13.93’
151º 14.18’
151º 13.14’
151º 41.20’
151º 43.00’
151º 45.88’
151º 43.03’
151º 46.32’
151º 43.92’
151º 45.03’
151º 35.17’
151º 36.42’
151º 35.83’
151º 33.38’
151º 34.74’
151º 32.56’
151º 33.06’
151º 19.35’
151º 19.67’
Soak Time
(h:mm)
2:30
3:47
4:22
4:50
2:54
3:21
3:58
3:16
3:22
3:34
1:35
3:00
3:20
2:38
3:25
3:34
3:38
2:27
3:15
3:51
2:32
2:40
3:12
2:41
3:15
2:56
3:12
2:44
3:04
3:19
2:34
3:13
3:21
3:00
3:20
3:39
394
Average
depth (fm)
33
29
29
33
35
33
35
33
32
33
28
44
36
39
41
34
21
31
36
29
57
21
45
51
53
31
47
37
16
58
47
50
53
53
40
30
Table 3. Catches in numbers and pounds (for legal sized halibut) during the 2007 Dogfish
mischmetal experiment.
Species or species group
Pounds
Halibut ≥82 cm
Count
Halibut ≥82 cm
Halibut <82 cm
Dogfish
Skates
Sculpins
Pacific Cod
Starfish
Others
Standard
‘C’
Gear
Dummy Mischmetal
‘D’
‘M’
Total
884.4
953.0
962.8
45
80
759
24
43
23
25
4
51
46
691
23
28
9
16
4
45
52
612
13
42
10
43
7
2,800.1
141
178
2062
60
113
42
84
15
Table 4. ANOVA table of dogfish catches in numbers.
Set
Treatment
Residuals
Df
35
2
70
Sum Sq
3,739.1
300.7
885.3
Mean Sq
106.8
150.3
12.6
F value
8.4469
11.8873
Prob (>F)
3.15e-14
3.59e-05
395
Figure 1. Circle hook with metal 4.5 cm on a side 0.7 cm thick triangle attached using an
electrical tie.
151°40'W
151°30'W
151°20'W
151°10'W
152
59°40'N
155
Homer
160
153
159
151
156
154
162
185
59°38'N
Homer Spit
184
161
59°40'N
150
59°38'N
169
163 158
166
165
167
168
59°36'N
164
Kachemak Bay
59°36'N
157
59°34'N
59°34'N
183 182
181
59°32'N
174
59°30'N
172
173
170
179
Cook
Inlet
176
175 171
59°32'N
Alaska
180
178 177
Kachemak Bay
59°30'N
Kodiak Island
Mercator
151°40'W
151°30'W
151°20'W
Figure 2. Fishing locations for the 2007 Dogfish Mischmetal experiment.
396
151°10'W
Homogeneity test for the Pacific sleeper shark (Somniosus
pacificus): Project update
Stephen Wischniowski
Trent Garner
Institute of Zoology, Zoological Society of London, Regent’s Park, United Kingdom
Caroline Cameron
Department of Biochemistry and Microbiology, University of Victoria, Canada
Abstract
A test of homogeneity will be conducted on Pacific sleeper shark (Somniosus pacificus)
samples from the north Pacific Ocean in an attempt to determine the genetic stock structure of
this species. Collections are represented by 118 tissue samples ranging from areas of high to low
shark occurrence within three IPHC charter regions. Extraction of mitochondrial DNA and PCR
amplification will commence in the winter of 2007.
Introduction
The population dynamics of Pacific sleeper sharks (Somniosus pacificus) within the northeast
Pacific are not well documented. Preliminary tagging studies have indicated that at least some
sleeper sharks display a resident behaviour, and likely have relatively small home ranges. To
test this assumption, tissue samples were collected during the 2004 International Pacific Halibut
Commission (IPHC) general setline survey. A simple test of homogeneity will compare samples
collected from regions of high species occurrence to peripheral regions of lesser occurrence.
Mitochondrial DNA polymorphisms will be used as the initial genetic marker system to investigate
genetic differentiation among the sampling locations. The objective of this study is to test if
mobility in sleeper sharks has led to genetic homogeneity within this sampling range. Alternately,
heterogeneity could indicate some degree of site fidelity. Knowing the population structure of a
species can be very useful when dealing with concerns of conservation. The IPHC general survey
has one of the best designs for encountering sleeper sharks over a wide area, and thus was solicited
to supply tissue samples for this experiment.
Results
Tissue samples were collected during the 2004 IPHC standardized setline survey. Biopsy
tips mounted on pole spears were utilized to collect tissue samples of approximately 5 by 100
mm in size. These were immediately placed in 2-ml micro-vials containing 95% EtOH. A total
of 118 samples were collected: 40 samples from the Unalaska charter region, 51 samples from
the Shelikof charter region, and 27 samples from the Ommaney charter region. Data collected
included date, charter region, station number, and animal’s condition. The animal’s condition was
397
based on whether the sample was collected from a dead specimen or a live specimen. Length and
sex data were also collected when possible.
Discussion
The extraction of mitochondrial DNA from tissue samples and polymerase chain reaction
(PCR) amplification of the DNA target chain will commence in winter 2007. We will initially
attempt amplification using primers located within the proline tRNA and 12S rRNA regions of
the mitochondria. These primers have been used to examine population genetic structure across
a similar geographic range in blacktip sharks (Charcharhinus limbatus) and yielded sufficient
information to differentiate among nurseries of this species. In the event that primers fail to function
for our species, we will use cytochrome b-specific primers. While this region will undoubtedly yield
lower polymorphism than the faster-evolving control region, the respective primers are known to
exhibit utility across a broad range of shark families and have previously exhibited point mutation
variability in three different shark species: the sandbar shark (Carcharhinus plumbeus), blue shark
(Prionace glauca), and the great white shark (Carcharodon carcharias).
Statistical analysis will be by way of χ2 and Analysis of Molecular Variance (AMOVA)
probabilities of haplotype homogeneity across sampling sites. As the name suggests, AMOVA is
a method for studying molecular variation within a species. AMOVA works on such data to create
a distance matrix between samples in order to measure the genetic structure of the population
from which the samples are drawn. In statistical terms, AMOVA is a testing procedure based on
permutational analysis and involves few assumptions about the statistical properties of the data.
The extraction of mitochondrial DNA has been delayed until the winter of 2007 because of
the unavailability of one of the co-investigators. This delay will also result in a laboratory change.
The extractions were to occur at the Laboratory for Infectious Diseases at the Department of
Medicine, University of Washington; however, this work will now follow the co-investigator to a
new facility operated by the Department of Biochemistry and Microbiology at the University of
Victoria, British Columbia.
398

Pages 309-398

Transcription

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