Advances in king crab juvenile biology: Growth

Advances in king crab juvenile biology: Growth

Advances in king crab juvenile biology:
Growth, life history, habitat, and predation
Ginny L. Eckert
University of Alaska Fairbanks,
Juneau Center School of Fisheries and Ocean Sciences
1
Graduate Students
Ben Daly
PhD Fisheries in progress
Jodi Pirtle
PhD Fisheries 2010
Miranda Westphal
MS Fisheries 2011
2
Background – Red King Crab Fishery
3
140
Total catch biomass (million lbs)
Bristol Bay
Red King Crab
Catch
Trawl bycatch
Pot bycatch---males
Cost recovery---U.S.
120
Pot bycatch---females
Retained---Foreign
Retained---U.S.
100
80
Handling mortality rate =
20% for pot &
80% for trawl
60
40
20
0
1953
NPFMC Crab SAFE 2010
1958
1963
1968
1973
1978 1983
Year
1988
1993
1998
2003
2008
Figure 2. Retained catch biomass and bycatch mortality biomass (million lbs) for Bristol Bay red king
crab from 1960 to 2009. Handling mortality rates were assumed to be 0.2 for the directed pot fishery and
0.8 for the trawl fisheries.
4
AI Crab SAFE
ret catch
total directed catch (oberved discard)
traw l bycatch
total directed catch (model estimated discard)
200
180
EBS
Snow Crab Catch
160
Catch (1000 t)
140
120
100
80
60
40
20
0
1975
1980
1985
1990
1995
2000
2005
2010
2015
Survey Year
Figure 1. Catch (1000 t) from the directed snow crab pot fishery and groundfish trawl bycatch. T
catch is retained catch plus discarded catch after 50% discard mortality
wasCrab
applied.
NPFMC
SAFEDiscard
2010 catc
estimated from observer data 1992 to present. Discard for 1978 to 1991 was estimated in the mod
5
Trawl bycatch is male and female bycatch from groundfish trawl fisheries with 80% mortality app
EBS Chionoecetes bairdi Retained Male Catch
50
Catch (1000T)
40
30
20
10
0
1965
1970
1975
1980
1985
1990
1995
2000
2005
Year
US Retained Catch
Russia Retained Catch
Japan Retained Catch
Total Retained Catch
Figure 5. Eastern Bering Sea Chionoecetes bairdi retained male catch in the directed United States,
Russian and Japanese fisheries, 1965-2010.
NPFMC Crab SAFE 2010
6
Background – Red King Crab Fishery
Six of eight stocks
closed to commercial
fishing
7
Background – Blue King Crab Fishery
8
Why have king crabs not recovered
in the absence of fishing?
• Recruitment limitation
• Overfishing - threshold effects
•Climate-driven fluctuations
• Regime shift - Predation
9
King Crab Life Cycle
Zoea 3
Zoea 4
Zoea 2
Zoea 1
Glaucothoe
Mating
Female with extruded eggs
Crab Instar 1
10
Juvenile Production
11
Hatchery Culture:
Juvenile Nursery
What do juvenile red king crab eat?
Reduce cannibalism
Optimize growth
Vary diet, density & substrate
12
B. Daly et al. / Aquaculture 293 (2009) 68–73
71
C1-C3
Diet
Density
Substrate
Diet*Density
Diet
Density
Substrate
Diet
Density
Substrate
Diet*Density
Daly et al. 2009 Aquaculture
Mean ± SE of A) survival, B) carapace width, and C) wet weight of red king crab juveniles reared using Cyclop-eeze®, Zeigler™ shrimp nursery feed, and frozen enriched
ia as diets at stocking densities of 500 m− 2, 1000 m− 2, and 2000 m− 2 with and without artificial substrate.
13
Color
Experiment - add nutritional supplements
Astaxanthin & Calcium
14
Hue Index
Color: Hue
Daly et al. in review
15
Survival
Survival
Daly et al. in review
16
Hatchery Culture:
Juvenile Nursery
Issues: Cannibalism
Size grading -- diet & density
17
Survival
Survival
Size Grading
Daly et al. in review
18
Survival
Survival
Size Grading
Daly et al. in review
19
Hatchery Culture:
Juvenile Nursery
Increasing survival:
• Complex substrates: reduces antagonistic interactions
20
Hatchery Culture:
Juvenile Nursery
Increasing survival:
• Complex substrates: reduces antagonistic interactions
• Size grading: reduces cannibalism on smaller crabs
21
Hatchery Culture:
Juvenile Nursery
Increasing survival:
• Complex substrates: reduces antagonistic interactions
• Size grading: reduces cannibalism on smaller crabs
• Diet supplements: increases nutrition
22
Hatchery Culture:
Juvenile Nursery
Increasing survival:
• Complex substrates: reduces antagonistic interactions
• Size grading: reduces cannibalism on smaller crabs
• Diet supplements: increases nutrition
• Stocking density: decreases cannibalism
23
Hatchery Culture:
Juvenile Nursery
Increasing survival:
• Complex substrates: reduces antagonistic interactions
• Size grading: reduces cannibalism on smaller crabs
• Diet supplements: increases nutrition
• Stocking density: decreases cannibalism
Increasing growth:
• Diet supplements: increases nutrition
24
Hatchery Culture:
Juvenile Nursery
Increasing survival:
• Complex substrates: reduces antagonistic interactions
• Size grading: reduces cannibalism on smaller crabs
• Diet supplements: increases nutrition
• Stocking density: decreases cannibalism
Increasing growth:
• Diet supplements: increases nutrition
• Density dependent growth: moderate density has best growth
25
Juvenile Growth Studies
Juvenile king crab growth during first year.
Are hatchery animals similar to wild ones?
26
27
Crab Growth
16
Hatchery crabs
Wild crabs
Carapace length (mm ± SD)
14
12
10
8
6
4
2
0
C1
C2
C3
C4
C5
Molt stage
C6
C7
C8
C9
!
Westphal et al. in prep
28
29
18
a.
Hatchery crabs
Wild crabs
Field crabs
Carapace length (mm ± SD)
16
14
12
*
*
*
10
*
8
6
4
2
0
2.0
1.8
b.
1.6
*
1.4
1.2
1.0
*
*
*
0.8
0.6
0.4
0.2
t
gu
s
Au
y
Ju
l
e
Ju
n
M
ay
ril
Ap
ch
M
ar
ry
ua
br
Fe
ua
ry
0.0
Ja
n
Spine length (mm ± SD)
*
Hatchery crabs
Wild crabs
Field crabs
Comparisons
with wild
crabs
!
Westphal et al. in prep
30
Juvenile Production
31
Nursery Habitat Function
• Nursery habitats should maximize survival
and growth
• Complex benthic habitat is important
–Why is structure important?
–Are certain habitats more valuable?
–What is the role of structure in survival?
32
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Habitat selection
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33
Experimental Substrata
Algae
Algae Mimic
Fouled Algae Mimic
Bryozoan
Bryozoan Mimic
Fouled Bryoz Mimic
Hydroid
Hydroid Mimic
Fouled Hydro Mimic
34
Competency of
Hatchery Juveniles
Lab Predation
Role of habitat
•
•
•
•
Sand
Hydroids
Hydroids/Macroalgae
Hydroid Mimics
Pirtle et al. in prep
35
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Habitat preferences in absence of predator
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Predation by cod in different habitats
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37
38
Laboratory Predation
Conclusions
• Structure increases survival with fish
predators
• Prefer biogenic habitats when predators
are absent
• Engage in refuge-seeking behavior when
predators are present
39
40
% survival
visual
exposure to
predators
complete
exposure to
predators
Daly et al. in prep.
41
Laboratory Predation
Conclusions
• Structure increases survival with fish
predators
• Prefer biogenic habitats when predators
are absent
• Engage in refuge-seeking behavior when
predators are present
• Predator defense learned.
42
Crab Tethering Methods
43
44
45
5m
5m
46
47
48
49
50
51
Habitat Treatments
Procedural Control
Structure
No Structure
52
Potential Predators Observed
Pacific cod
Walleye pollock
Arctic shanny
Northern ronquil
Kelp greenling
Alaskan ronquil
Whitespotted greenling Decorated warbonnet
Dusky rockfish
Crescent gunnel
Quillback rockfish
English sole
Copper rockfish
Yellowfin sole
Sculpins
Starry flounder
Buffalo sculpin
Giant Pacific octopus
Great sculpin
Hermit crabs
Crested sculpin
Helmet crab
Silverspotted sculpin
Decorator crab
Red Irish lord
Red king crab
Pycnopodia seastar
Sturgeon poacher
53
Pacific cod
Arctic shanny
Observed in Video
Walleye pollock
Northern ronquil
Kelp greenling
Alaskan ronquil
Whitespotted greenling Decorated warbonnet
Dusky rockfish
Crescent gunnel
Quillback rockfish
English sole
Copper rockfish
Yellowfin sole
Sculpins
Starry flounder
Buffalo sculpin
Giant Pacific octopus
Great sculpin
Hermit crabs
Crested sculpin
Helmet crab
Silverspotted sculpin
Decorator crab
Red Irish lord
Red king crab
Pycnopodia seastar
Sturgeon poacher
54
Observed Predation
Pacific cod
Walleye pollock
Arctic shanny
Northern ronquil
Kelp greenling
Alaskan ronquil
Whitespotted greenling Decorated warbonnet
Dusky rockfish
Crescent gunnel
Quillback rockfish
English sole
Copper rockfish
Yellowfin sole
Sculpins
Starry flounder
Buffalo sculpin
Giant Pacific octopus
Great sculpin
Hermit crabs
Crested sculpin
Helmet crab
Silverspotted sculpin
Decorator crab
Red Irish lord
Red king crab
Pycnopodia seastar
Sturgeon poacher
55
Observed Predation
Alaskan ronquil
Sculpins
Buffalo sculpin
Pycnopodia Seastars
56
Crab Field Survival
100
Crab survival (%)
80
Structure
p < 0.0001
No Structure
Structure
Control
Stage p = 0.07
60
40
20
0
0
Age-0
Age-1
Crab Stage
Pirtle et al. in review
57
58
Field Predation
Conclusions
• Structure increases survival with a variety
of predators in the field
• Structure, cryptic behavior, and direct
defense improve survival in the field
• Role of groundfish predation is
questionable
59
Why have king crabs not recovered
in the absence of fishing?
• Recruitment limitation
• Overfishing - threshold effects
•Climate-driven fluctuations
• Regime shift - Predation
60
Blue King Crab
61
Future Studies
• Fish predation - Gut content analysis
• Habitat studies
• Larval & juvenile king crab recruitment in Bristol Bay
• Blue king crab
62
Thanks to AKCRRAB
supporters!
63