evaluation of current management practices

EVALUATION OF CURRENT MANAGEMENT PRACTICES
AND ASSESSMENT OF RECRUITMENT, GROWTH AND
CONDITION OF WALLEYES IN TENNESSEE RESERVOIRS
A Final Report
Presented to the
Tennessee Wildlife Resources Agency
by
Christopher J. Vandergoot, M.S. and Phillip W. Bettoli, Ph.D.
U.S. Geological Survey, Biological Resources Division
Tennessee Cooperative Fisheries Research Unit
Tennessee Technological University
Cookeville, TN 38505
October 2001
EXECUTIVE SUMMARY
1. Tennessee’s walleye stocking program was evaluated by releasing fry and
fingerlings marked with oxytetracycline (OTC). Marking efficacy was high (> 99%)
for walleyes immersed in 500 mg/L OTC for 6 hours and mortality was negligible.
Subsequent recaptures of age-1 walleyes revealed that little or no natural reproduction
occurred in 1999 and 2000 in the five study reservoirs (Center Hill, Norris, South
Holston, Tellico, Watauga). The contribution of stocked walleyes to those two year
classes ranged between 92 and 100%.
2. Adult walleyes were sampled with experimental gill nets in six reservoirs (the five
mentioned above and Dale Hollow). The oldest walleyes (up to age-21) were in
Watauga Reservoir; the youngest population was in Center Hill Reservoir, where only
one fish was older than age-4. The age-class structure in the six reservoirs indicated
that most of the walleye fisheries were dependent on TWRA’s stocking program
because natural reproduction was usually low or inconsistent over the last decade.
3. Trout stocking rates and threadfin shad catch rates together explained a significant
amount of variation among reservoirs in adult walleye robustness. The heaviest
walleyes were in South Holston, Dale Hollow and Watauga Reservoirs. Significant
between-year variation was also detected for four of the six populations sampled.
4. No threadfin shad were collected in Watauga Reservoir, but they were caught in
similar numbers in the other five reservoirs. Alewives were in all six reservoirs and
their catch rates varied significantly; mean catch rates were higher in Watauga and
Dale Hollow (207-300/net night) than in the other four reservoirs (7-23 /net night).
5. Walleyes grew rapidly in all reservoirs; the average time to reach 406-mm total
length ranged from 1.7 to 2.1 years.
6. Fishery yields under different minimum size limits were simulated using the
Beverton-Holt equilibrium yield model. Three size limits (381-, 406-, and 457-mm
total length) increased yield in all reservoir compared to no size limit at most levels of
exploitation when conditional natural mortality rates were low (< 20%). At higher
natural mortality rates, the benefits of a minimum size limit were eliminated. The
observed longevity of walleyes (maximum age averaged 13 years over all reservoirs)
indicated that natural mortality rates were low; thus, minimum size limits were
appropriate management actions in all reservoirs. Although yield was usually highest
under a simulated 457-mm length limit, the benefits were slight unless conditional
fishing mortality rates were high (> 40%) and natural mortality rates were low (10%).
7. Only one walleye population (Center Hill) exhibited characteristics of heavy
exploitation. Although most populations were sustained through a stocking program,
the abundance and size structure of most populations was excellent. Large variations
among reservoirs in walleye robustness and forage abundance suggested that stocking
rates should be matched to the supply of available forage.
2
FOREWORD
This final report is based on a Master of Science thesis prepared by the senior author.
The report is organized into three chapters. Chapter I evaluated the contribution that
stocked walleyes make to year-class strength in Tennessee reservoirs. Chapter II
describes and compares the growth and condition of walleyes in six Tennessee reservoirs.
Chapter III presents results pertaining to simulated fishery yields as a function of
different minimum size limit regulations.
Tables and figures cited in each chapter are presented at the end of each chapter. All
references cited in each chapter were pooled and are presented at the end of Chapter III.
ACKNOWLEDGEMENTS
Primary funding for this research was provided by the Tennessee Wildlife Resources
Agency. Additional support was provided by the Center for the Management,
Utilization, and Protection of Water Resources at Tennessee Technological University
and the Tennessee Cooperative Fishery Research Unit.
Numerous individuals from the Tennessee Wildlife Resources Agency contributed to the
success and completion of this project. In particular, we wish to thank Tim Churchill,
Mike “Stump” Smith, Doug Peterson, and Anders Myhr for their knowledge of the
history of walleye management in Tennessee and their insight into this project. We also
want to thank Ernie Poore, Mark Thurman, Jim Negus, and hatchery personnel at Eagle
Bend and Normandy fish hatcheries for assisting with data collection. Tom Hampton of
the Virginia Department of Game and Inland Fisheries also assisted with data collection
on South Holston Reservoir.
We are grateful for the dedicated assistance rendered in the field and in the laboratory by
students and staff of Tennessee Tech, particularly Paul Horner, Dan Isermann, Shawn
Banks, Mike Luisi, and Jason Henegar.
This report benefited from the constructive comments made on earlier drafts by Drs.
Bradford Cook and Daniel Combs of the Department of Biology, Tennessee
Technological University.
3
TABLE OF CONTENTS
Page
CHAPTER
I. Stocking Contribution of Hatchery-Reared Walleyes...................................... 5
Introduction............................................................................................... 5
Methods .................................................................................................... 7
Results....................................................................................................... 8
Discussion .................................................................................................10
Tables........................................................................................................11
II. Population Characteristics and Abundance of Clupeid Forage Fish...............16
Introduction...............................................................................................16
Methods ....................................................................................................18
Results.......................................................................................................19
Discussion .................................................................................................21
Tables........................................................................................................23
Figures ......................................................................................................27
III. Evaluation of the Current Minimum Size Limits for Walleyes.....................32
Introduction...............................................................................................32
Methods …………………………………………………………………33
Results.......................................................................................................35
Discussion .................................................................................................36
Tables........................................................................................................38
Figures ......................................................................................................41
IV. Management Implications ..........................................................................53
LITERATURE CITED ………………………………………………………………… 55
APPENDICES ..................................................................................................................66
4
CHAPTER I
STOCKING CONTRIBUTION OF HATCHERY-REARED WALLEYES
ABSTRACT
The Tennessee Wildlife Resources Agency annually stocks walleyes Stizostedion
vitreum in several Tennessee reservoirs to sustain those fisheries; however, the efficacy
of this program has never been thoroughly evaluated. In 1999 and 2000, stocked
walleyes were marked with oxytetracycline (OTC) to distinguish hatchery-reared walleye
from wild fish. Marking efficacy was high (99%) for larval and juvenile walleyes
immersed in 500 mg OTC/ L for 6 h. The contribution of stocked walleyes to the 1999
and 2000 year-classes in Center Hill, Norris, South Holston, Tellico, and Watauga
Reservoirs was high (92-100%) in each reservoir. Marking walleyes with OTC was an
effective technique to identify hatchery-reared fish in Tennessee reservoirs.
INTRODUCTION
Numerous studies investigating the effectiveness of stocking walleyes
Stizostedion vitreum in North America exist (e.g., Murphy et al. 1983; Fielder 1992).
Although stocking walleyes is often successful in establishing new walleye populations
(Kraai et al. 1983) or supplementing natural recruitment (Forney 1975), merely stocking
walleyes is not a guarantee of success. For example, in a review of walleye stocking case
histories, Laarman (1978) reported only one-third of all supplemental stockings were
effective. Similarly, Ellison and Franzin (1992) reported success rates ranging from 32 to
50% when walleyes were stocked at various stages of development (i.e., as fry and
fingerlings). Research has also focused on the variables associated with the success or
failure of stocking walleyes. Factors contributing to stocking effectiveness include size
of fish stocked (Koppelman et al. 1992; Mitzner 1992), food availability (Mathias and Li
1982), reservoir hydrology (Willis and Stephen 1987) and initial post-stocking mortality
(Hoxmeier et al. 1999). It is relatively easy to evaluate stocking programs where walleye
populations did not exist prior to stocking; however, it becomes more difficult in systems
where natural reproduction in known to occur.
Two general techniques have been utilized to evaluate contributions of hatchery
produced walleyes. The first technique involves stocking walleye fry in alternating years
(Carlander 1960; Forney 1975); biologists then compare the catch of young-of-the-year
walleyes during stocking and non-stocking years. However, this technique fails to
accurately measure the contribution of stocked walleyes in lakes and reservoirs where
natural recruitment occurs. An alternative method of assessing hatchery contributions
involves marking fish prior to stocking using genetic marks (Murphy et al. 1983;
Koppelman et al. 1992) or physical tagging (Forney 1963; LaJeone and Bergerhouse
1991). Numerous techniques have been developed to mark and tag adult fishes (e.g., Guy
et al. 1996); however, the options available to mark larval and juvenile fish are not as
diverse. Walleye fingerlings have been freeze-branded (LaJeone and Bergerhouse 1991)
and marked with coded-wire tags (Parsons et al. 1994) to distinguish hatchery-produced
walleyes from offspring originating from natural reproduction. Although these
5
techniques have been successfully used to evaluate stocking contribution of fingerlings
(Lucchesi 1997), mortality associated with handling fish has been observed (Schreiner
1985; Parsons et al. 1994). Mass-marking stocked fish via chemical immersion enables
biologists to mark walleyes as fry and eliminates handling individual fish (Brooks et al.
1994).
Weber and Ridgeway (1962) mass-marked hatchery-reared Pacific salmon
Oncorhyncus spp. and rainbow trout O. mykiss with tetracycline antibiotics, which
produced a yellow-gold florescent band on calcified structures (e.g., vertebrae, ribs and
otoliths). Researchers have validated the use of oxytetracycline (OTC) in evaluating the
contribution of hatchery reared fish for numerous fish species, including American shad
Alosa sapidissima (Lorson and Mudrak 1987; Hendricks et al. 1991), striped bass
Morone saxatilis (Secor et al. 1991; Reinert et al. 1998), black crappies Pomoxis
nigromaculatus (Conover and Sheehan 1999; Isermann et al. 1999), saugers Stizostedion
canadense (Heidinger and Brooks 1998) and walleyes (Scidmore and Olsen 1969; Brooks
et al. 1994; Lucchesi 1999). Although Dabrowski and Tsukamoto (1986) and Lorson and
Mudrak (1987) observed mark deterioration, mark persistence is generally long enough
(> 1 year) for a stocking contribution study to be performed (Reinert et al. 1998;
Heidinger and Brooks 1998) and Peterson and Carline (1996) failed to observe a
difference in survival between OTC-marked and unmarked walleye fry. Similarly,
Weber and Ridgeway (1967) reported tetracycline marking did not adversely affect
growth and survival of Pacific salmon.
Native self-sustaining walleye populations existed in the Cumberland and
Tennessee rivers prior to the impoundment of these rivers in the early and mid- 1900’s
(Hackney and Holbrook 1978). After impoundment, some populations were unable to
reproduce in the lentic environments and progeny from Great Lakes walleye stocks were
introduced to re-establish spawning populations (Muench 1966; Libbey 1969). Selfsustaining walleye populations were established in reservoirs where walleyes were native
prior to impoundment (e.g., Center Hill, Dale Hollow and Norris reservoirs) and new
self-sustaining populations were also established (e.g., South Holston and Watauga
reservoirs; D. Peterson; Tennessee Wildlife Resources Agency [TWRA]; personal
communication). However, natural recruitment declined again within several decades in
two reservoirs (Dale Hollow and Watauga), coinciding with the introduction of alewives
Alosa pseudoharengus (Schultz 1992; D. Peterson; TWRA; personal communication).
Although attempts were made to re-establish self-sustaining populations, they were
unsuccessful and supplemental stockings were necessary to maintain some walleye
fisheries.
The TWRA annually stocks about 500,000 walleyes; however, the efficacy of this
management program is unknown. The objectives of this study were to (1) evaluate the
efficacy of marking walleyes in TWRA fish hatcheries; and (2) assess the contribution of
OTC-marked walleye fry and fingerlings in several Tennessee reservoirs where natural
recruitment once sustained these fisheries.
6
METHODS
Oxytetracycline Marking
Larval and juvenile walleyes were marked with OTC prior to being stocked in six
Tennessee reservoirs (Table 1). Walleye fry (3-5 d post-hatch) and fingerlings hatched
and reared at three Tennessee State Fish Hatcheries (Eagle Bend, Normandy, and
Springfield) and one Virginia State Fish Hatchery (Buller) were immersed in a 500 mg
OTC/ L bath as described by Brooks et al. (1994). Prior to loading walleye fry and
fingerlings on the stocking truck, a slurry of OTC was mixed, buffered and added to the
hauling tanks (587-1,779 L). After the walleyes were loaded, they remained in the slurry
of OTC for 6 h before being stocked. During this period, temperature and dissolved
oxygen were monitored in each hauling tank. A water sample was taken from each
hatchery and analyzed for alkalinity (CaCO3 mg/ L), total calcium (mg/ L), hardness (mg/
L), total magnesium (mg/ L), conductivity (µS/cm) and pH. Prior to stocking, 50
fingerlings were measured (total length; mm). To fulfill stocking quotas in 1999 and
2000, the TWRA obtained additional walleye fingerlings from the Minor Clark Fish
Hatchery, Kentucky. Walleye fingerlings from Minor Clark were OTC marked as fry in
500 mg OTC/ L and 700 mg OTC/ L baths in 1999 and 2000, respectively.
In March 1999 and 2000, walleye fry were marked with OTC at Eagle Bend Fish
Hatchery and stocked into Doakes Pond, a 2.8 ha sub-impoundment on Norris Reservoir.
Doakes Pond is used as a supplemental rearing facility by TWRA hatchery personnel;
fathead minnows Pimephales promelas were stocked into Doakes Pond after the natural
forage (i.e., zooplankton and ichthyoplankton) was depleted by the juvenile walleyes.
Advanced walleye fingerlings (70-175 mm; TL) were harvested during September and
released into the Davis Creek embayment of Norris Reservoir.
Marking Efficacy
Marking efficacy was determined by retaining a sample (n=300) of walleye
fingerlings marked with OTC from each hatchery, reservoir, stocking site and date.
Following immersion in OTC, walleye fingerlings were held in re-circulating tanks (5681,136 L) and fed a diet of frozen brine shrimp (Colesante 1996). About 40 fingerlings
from each reservoir and stocking site were subsequently sacrificed 21 d later and their
sagittal otoliths were removed, cleaned and stored in 7 mL plastic vials to prevent OTC
mark deterioration (Choate 1964). Otoliths were mounted on microscope slides with
QuickTite Super Glue containing cyanoacrylate (Secor et al. 1991). Mounted otoliths
were viewed under a Nikon Optiphot-2 compound microscope equipped with a 100 W
ultraviolet light source and a Nikon B3-A filter cube (450−490-nm excitation filter, a
515-nm barrier filter, and a 510-nm dichroic mirror). Whole otoliths were wet-ground
with 600-grit sandpaper when necessary to detect OTC marks.
A sample (n=40) of walleye fingerlings from Minor Clark Fish Hatchery was
frozen on the day of stocking and later measured; sagittal otoliths were removed,
mounted, and examined for OTC marks. The fingerlings stocked into Norris and Tellico
reservoirs in May 2000 were marked as fry on the same day in March; thus, marking
7
efficacy for Minor Clark Fish Hatchery fingerlings stocked in May 2000 was assumed to
be identical.
Walleye fry were marked with OTC at Eagle Bend Fish Hatchery and stocked
into Tellico Reservoir in 1999. A sample (n= 500) was held in 38-L aquaria to evaluate
OTC mark efficacy. At the end of twelve days, the remaining fry (n=15) were sacrificed,
and sagittal otoliths were removed and examined for OTC marks. Oxytetracyline marks
were visible without polishing.
A sample (n=40) of advanced fingerlings from Doakes Pond was retained when
the pond was harvested in September 1999. In June 2000, a sample (n=38) was taken by
electrofishing the shoreline of Doakes Pond.
Stocking Contribution
Age-1 walleyes stocked in May each year (1999 and 2000) and sampled the
following winter (December-February) were collected with experimental gill nets from
Center Hill, Norris, Tellico, South Holston and Watauga reservoirs. In 1999, two
different monofilament gill net types (A and B; Table 2) were used to collect walleye; an
additional net type (C) was incorporated in 2000 to target age-1 walleye. Gill nets were
set perpendicular to the shoreline on gradually tapering, rocky points throughout each
reservoir. Due to the crepuscular nature of walleyes (Ryder 1977), nets were deployed
before dusk and retrieved the following morning. Upon retrieval, net location and mesh
size for each walleye presumed to be age-1 were recorded. Walleyes were then
measured, weighed, sexed and sagittal otoliths were removed. Otoliths were cleaned and
placed in a 7 mL plastic vial until they were aged. After walleye otoliths were examined
to confirm the age of the fish (Erickson 1983), an otolith from each age-1 walleye was
mounted and examined for an OTC mark as previously discussed.
South Holston Reservoir is managed and stocked cooperatively by the TWRA and
Virginia Department of Game and Inland Fisheries (VDGIF). In conjunction with the
regional fishery biologist from the VDGIF, age-1 walleyes were collected by
electrofishing twenty transects throughout the reservoir at night in November 2000.
Transects were established on shallow rocky points and electrofished for 10 min.
Walleyes less than 350 mm were measured and weighed and sagittal otoliths were
removed, aged and examined for OTC marks.
Stocking contribution at age-2 was also assessed for walleyes stocked in May
1999 in South Holston and Watauga reservoirs because insufficient numbers were
collected as age-1 fish. Fisheries biologists with the Tennessee Valley Authority and
TWRA collected age-2 walleyes with experimental gill nets (Type D; Table 2) in
November and December 2000.
RESULTS
Size and Stocking Density
Three size classes of OTC-marked walleye were stocked into six Tennessee
Reservoirs in 1999 and 2000. The only fry stocking occurred in 1999 when walleye fry
were stocked in Tellico Reservoir at a density of 154 fry/ ha (Table 3). Mean length at
8
stocking of walleye fingerlings ranged between 33 and 41 mm; stocking rates ranged
between 11-64 fingerlings/ ha in 1999 and 2000. Advanced fingerlings that were reared
in Doakes Pond were stocked into Norris Reservoir at a rate of 0.4 fingerlings/ ha and
averaged 89 and 127 mm at release in September 1999 and September 2000, respectively.
Marking Efficacy
Water quality at the five fish hatcheries varied with respect to alkalinity, total
calcium, total magnesium, hardness, conductivity and pH (Table 4); however, marking
efficacy was high (mean=99%) for all walleyes immersed in OTC (Table 5). Marking
efficacy was 100% for walleyes marked and stocked as fry in Tellico Reservoir, 1999.
Similarly, marking efficacy was high (mean=98%) for walleyes marked as fry and
stocked as fingerlings from Eagle Bend and Minor Clark fish hatcheries in 1999 and
2000. Walleyes marked and stocked as fingerlings also retained the OTC well
(mean=99%; Table 5). Despite the high marking efficacy observed in walleyes marked
as fry, OTC marks were easier to distinguish in walleyes marked as fingerlings than those
marked as fry. In a blind experiment (n=40), all of the otoliths known to be marked with
OTC were correctly identified.
Contribution of Stocked Walleyes
Contribution of hatchery-reared walleyes was high (mean 98%) for all study
reservoirs in 1999 and 2000 (Table 6). Although stocking contribution was 100% for
age-1 walleyes collected from the 1999 year-class in South Holston, Tellico and Watauga
reservoirs, these estimates were derived from small samples consisting of less than 10
fish per sample. About 1 million walleye fry were marked and stocked into Tellico
Reservoir in 1999, but only two age-1 walleyes were captured the following winter and
they were both OTC marked. Similarly, the 100% stocking contribution for the 1999
year-class in South Holston Reservoir was derived from a sample of only 9 fish collected
as age-1 and age-2 fish. Only two age-1 walleyes from the 1999 year-class in Watauga
Reservoir were captured; however, 51 of 54 age-2 walleyes collected from the 1999 yearclass were marked with OTC, indicating that stocking contribution was high (94%) for
that year-class. Nearly all (99%) age-1 walleyes from the 2000 year-class collected in
Center Hill and South Holston reservoirs originated from fingerlings stocked the previous
spring.
Walleye fingerlings stocked in 1999 and 2000 made a significant (>90%)
contribution to the 1999 and 2000 year-classes of age-1 walleyes in Norris Reservoir
(Table 6). Fingerlings were stocked from three different sources both years and their
contribution varied each year (Table 7). Similar numbers of walleye fry were stocked in
Doakes Pond each year; advanced fingerlings released in September 1999 made a
negligible contribution to that year-class, but a substantial contribution (14%) to the 2000
year-class (Table 7). Stocked fingerlings originating from Eagle Bend Hatchery, Minor
Clark Hatchery, and Doakes Pond contributed to the 1999 and 2000 year-classes in
similar proportions to which they were stocked (df=1, 4; F= 71.8; r2=0.96; P<0.01).
9
DISCUSSION
Immersing walleyes in 500 mg OTC/ L for 6 h effectively marked hatchery-reared
walleye fry and fingerlings in southern U.S. fish hatcheries. The efficacy of batch
marking walleyes with OTC has been variable in other locales. The efficacy of marking
walleye fry (2-4 d posthatch) and fingerlings in South Dakota with 500 mg/L OTC for 6 h
was 50 and 100%, respectively (Lucchesi 1997); mark retention was improved by
marking older walleye larvae (> 4 d posthatch) and increasing the concentration of OTC
to 700 mg/ L. The hard water (~300 mg CaCO3/ L) in the South Dakota study was
thought to reduce the ability of walleye fry to incorporate OTC into their sagittal otoliths.
Lucchesi (1997) theorized the softer water (60-100 mg/L) in the experiments conducted
by Brooks et al. (1994) may have facilitated the uptake of OTC. Marking efficacy was
high (mean=99%) in soft and moderately hard water in the present study, supporting the
theory of Lucchesi (1999) that water hardness influences OTC marking efficacy.
Juvenile walleyes were first stocked in Tennessee reservoirs in 1954 (Fetterolf
1956) and are currently stocked where natural recruitment is limited or non-existent. In
the past, this management practice has been evaluated indirectly on the basis of whether
or not year-classes were formed during stocking years (e.g., Carlander et al. 1960), rather
than the contribution of hatchery-reared fish to the fishery. Based on the recapture of
OTC-marked walleyes in this study, stocked fingerlings represented nearly all of the
walleyes in one or more year classes in all five study reservoirs. Similar results have
been reported for other reservoirs (Murphy et al. 1983; Fielder 1992; Koppelman et al.
1992) and natural lakes (Laarman 1978; McWilliams and Larscheid 1992; Lucchesi
1999) across North America. Walleye fingerlings in Tennessee are usually stocked at a
rate of 12-24 fingerlings/ ha; the exact rates are subject to hatchery production constraints
and stocking priorities (T. Churchill, TWRA, personal communication), similar to the
rates in Iowa (McWilliams and Larscheid 1992) and Missouri (Koppelman et al. 1992),
but substantially lower than in South Dakota (247/ha; Lucchesi 1999). Stocking
hatchery-reared walleyes at a rate of 12-24 fingerling/ ha was an effective management
strategy to augment natural recruitment in four Tennessee reservoirs. Walleye yield
ranged between 0.72 and 1.4 kg/ha in Center Hill, Dale Hollow, Norris, South Holston
and Watauga reservoirs in 2000 (Malvestuto and Black 2001) and compared to other
walleye populations in North America, walleye yields in Tennessee reservoirs are ranked
as fair to good (D. Baccante, personal communication, Ministry of Environment, Lands
and Parks, British Columbia, Canada).
Natural recruitment of walleyes is often affected by reservoir hydrology and
strong walleye year-classes are usually associated with high spring water levels
(Chevalier 1977; Kallemeyn 1987) except during years of extremely high discharges
(Willis and Stephen 1987). Sammons and Bettoli (2000) reported a positive relationship
between reservoir hydrology and year-class strength of saugeyes (Stizostedion vitreum x
S. canadense) and four other species in Normandy Reservoir, a tributary impoundment on
the lower Tennessee River. Native walleyes in the southern U.S. were considered to be
obligate river spawners, having specific well-defined spawning grounds (Hackney and
Holbrook 1978) and hydrology may still be crucial to spawning success in a reservoir
such as Center Hill, where some reproduction may still be occurring. Future stocking
assessments should include a cycle of ‘wet’ and ‘dry’ years to determine whether natural
10
recruitment is occurring and how it might affect the contribution of hatchery-reared
walleyes.
11
Table 1. Physical and biological characteristics of five Tennessee reservoirs. Data complied from Myhr et al. (1998a, 1998b),
Peterson and Negus (1998a, 1998b) and Peterson and Thurman (1998a, 1998b).
Year
impounded
Area
(ha)
Mean depth
(m)
Hydraulic
retention time
(d)
Mean annual
fluctuation
(m)
Chlorophyll-a
(mg/ L)
Center Hill
1948
9,224
22
131
9
8.8
Eutrophic
Norris
1936
13,680
18
245
18
2.4
Oligotrophic
South Holston
1950
3,032
27
340
12
4.2
Mesotrophic
Tellico
1980
6,503
8
37
2
6.2
Mesotrophic
Watauga
1948
2,572
27
400
13
4.0
Mesotrophic
Reservoir
1
Forsberg and Ryding (1980)
12
Trophic State1
Table 2. Dimensions of experimental horizontal gill nets used to collect age-1 walleyes
from five Tennessee reservoirs in 1999 and 2000.
Length X height
(m)
Net type
Mesh sizes
(mm; bar measure)
A
30.5 X 2.4
13, 19, 25, 32
B
45.7 X 2.4
19, 25, 38, 19, 25, 38
C
60.9 X 1.8
19, 25, 19, 25, 19, 25, 19, 25
D
30.5 X 1.8
25, 38, 51, 64, 76
Table 3. Date (month/ year), stocking rate (number / ha) and mean total length of
walleyes marked with oxytetracycline and stocked into six Tennessee reservoirs in 1999
and 2000. Standard deviation in parentheses.
Reservoir
Center Hill
Norris
Date stocked
Number
stocked
Stocking
rate
Mean total
length (mm)
9,224
May 2000
195,328
21
41 (4.1)
13,680
May 1999
329,868
24
44 (6.8)
≈ 5,000
0.4
89 (n/a)
342,465
25
43 (6.3)
≈ 5,000
0.4
127 (n/a)
May 1999
39,508
13
36 (4.9)
May 2000
146,360
48
33 (2.4)
1,000,000
154
.
May 2000
71,733
11
41 (3.3)
May 1999
97,828
38
40 (5.5)
Area (ha)
Sept. 2000
1
May 2000
Sept. 2000
South Holston
Tellico
Watauga
1
2
3,032
6,503
2,572
1
March 19992
Stocked as fry into Doakes Pond and released as advanced fingerlings
Stocked as fry (3-5 day post-hatch)
13
Table 4. Alkalinity (mg CaCO3/ L), total calcium (mg/ L), hardness (mg/ L), total
magnesium (mg/ L), conductivity (µS/cm) and pH for water at fish hatcheries where
walleye were marked with oxytetracycline in 1999 and 2000.
Hatchery
Buller, VA
Alkalinity
Total
calcium
Total
magnesium
Hardness
Conductivity
pH
71
15.8
7.9
72
169
7.7
Eagle Bend,
TN
100
25.4
11.0
107
258
7.9
Minor Clark,
KY
13
14.6
5.7
.
162
7.8
Normandy,
TN
40
13.2
2.0
41
101
7.5
Springfield,
TN
130
46.2
7.8
148
336
7.1
14
Table 5. Marking efficacy for walleyes marked with oxytetracycline (OTC) and stocked
into six Tennessee reservoirs, 1999 and 2000. Walleyes were stocked by Eagle Bend
Fish Hatchery, Normandy and Springfield state fish hatcheries in Tennessee, Minor Clark
State Fish Hatchery in Kentucky and Buller State Fish Hatchery in Virginia.
Reservoir
Hatchery
Number
marked
Size
marked
Number
examined for
OTC marks
Marking
efficacy
1999
Norris
Eagle Bend
Eagle Bend
Minor Clark
500,000
179,449
150,419
fry1
fingerling
fry1
40
47
40
93
96
100
South Holston
Eagle Bend
39,508
fingerling
40
100
Tellico
Eagle Bend
1,000,000
fry
15
100
Watauga
Eagle Bend
97,828
fingerling
42
98
2000
1
Center Hill
Normandy
Springfield
94,802
100,526
fingerling
fingerling
40
40
100
100
Norris
Eagle Bend
Eagle Bend
Minor Clark
400,000
313,564
28,901
fry1
fingerling
fry1
37
40
40
100
100
98
South Holston
Buller
146,360
fingerling
40
100
Tellico
Minor Clark
fry1
37
100
71,733
walleye fingerlings marked as fry and examined for OTC marks as fingerlings
15
Table 6. Stocking contribution of juvenile walleyes marked with oxytetracycline in five
Tennessee reservoirs,1999 and 2000.
Reservoir
Year
stocked
Age at
collection
Number
collected
Number
marked
Stocking
contribution
(%)
Center Hill
2000
1
124
123
99
Norris
1999
2000
1
1
96
146
88
144
92
99
South Holston
1999
1999
2000
1
2
1
2
7
78
2
7
77
100
100
99
Tellico
1999
1
2
2
100
Watauga
1999
1999
1
2
2
54
2
51
100
94
Table 7. Contribution of walleyes stocked into Norris Reservoir in 1999 and 2000
number of recaptures indicated in parentheses.
Source
Percent of total
number stocked
Number stocked
Percent of
recaptures
1999 (n=96)
Doakes Pond
Eagle Bend
Minor Clark
≈ 5,000
179,449
150,419
1
54
45
2
47
51
1
90
9
14
77
9
2000 (n=146)
Doakes Pond
Eagle Bend
Minor Clark
≈ 5,000
313,564
28,901
16
CHAPTER II
WALLEYE POPULATION CHARACTERISTICS
AND ABUNDANCE OF CLUEPID FORAGE FISH
ABSTRACT
Walleye robustness, size-structure, and age-structure and the abundance of
alewives Alosa pseudoharengus and threadfin shad Dorosoma petenense were assessed in
six Tennessee reservoirs. Walleyes were most robust in three reservoirs that were stocked
with rainbow trout Oncorhyncus mykiss and brown trout Salmo trutta at rates of 7 or
more trout/ ha (Dale Hollow, South Holston, and Watauga Reservoirs) and least robust in
reservoirs that received few or no trout (0-2 trout/ ha; Center Hill, Norris, and Tellico
Reservoirs). Trout stocking rates alone did not explain a significant amount of the
variation in walleye robustness (P=0.13), but a multiple regression model that included
threadfin shad catch rates was significant (df=2,5; F=5.3; r2=0.78; P=0.10). Stockpiling
of fish below the minimum length limit was not observed in any reservoir. The oldest
walleye was age-21 (Watauga Reservoir); the youngest population was in Center Hill,
where only one walleye was older than age-4. The geometric mean catch of alewives in
vertical gill nets was highest (> 200 fish/ net-night) in Dale Hollow and Watauga
Reservoirs where alewives were introduced by the TWRA in 1976; catches were lowest
(< 25 fish/ net-night) in Center Hill, Norris, South Holston, and Tellico Reservoirs, where
the populations were more recently established via illegal or accidental introductions.
Threadfin shad were caught at similar rates in the five reservoirs where they occurred.
INTRODUCTION
Prior to the construction of flood control and hydroelectric dams on the
Cumberland and Tennessee Rivers, walleyes Stizostedion vitreum were self-sustaining in
these drainages (Hackney and Holbrook 1978). Walleye populations initially thrived
after impoundment in many reservoirs, but declined within a few decades. Selfsustaining walleye populations were subsequently re-established with progeny from
Great Lakes walleye stocks in the 1960’s (Fetterolf 1956; Muench 1966;Libbey 1969). A
second decline in walleye recruitment in several Tennessee reservoirs coincided with the
introduction of alewives Alosa pseudoharengus, which were stocked to provide a stable
forage for coldwater sportfish species (Daniel 1984; Schultz 1992). Since the late
1980’s, larval and juvenile walleyes have been stocked to maintain several populations
(T. Churchill, TWRA, personal communication).
In the southeastern United States, forage fish were stocked in many reservoirs
because native forage species were often unsuitable as prey for resident and stocked
predators (Noble 1981). Gizzard shad Dorosoma cepedianum are native to the lower
17
Cumberland and Tennessee rivers (Evermann 1915; Etnier and Starnes 1993) and
flourished in several tributary reservoirs after impoundment. Although gizzard shad
possess several qualities of a suitable forage species (i.e., they are prolific and trophically
efficient), they often grow too large for most predators to utilize them as forage (Ney
1981). In many southern impoundments gizzard shad and threadfin shad D. petenense
are the most common forage fish species (Noble 1981; Ney et al. 1982).
Threadfin shad and alewives are two non-native forage fish species introduced
into southeastern impoundments. Prior to their introduction in the 1950’s by the
Tennessee Game and Fish Commission (Fetterolf 1956), threadfin shad were absent from
fish surveys conducted on the Cumberland and Tennessee rivers (Kirsch 1891; Evermann
1915). Similar to gizzard shad, threadfin shad also exhibit positive and negative
attributes as a forage species. Threadfin shad are prolific and remain vulnerable to
predation throughout life (Noble 1981); however, complete or partial winterkills occur
when water temperatures fall below 9οC for prolonged periods (Strawn 1963). Thus,
threadfin shad populations are prone to annual and extreme fluctuations in abundance.
Early introductions of threadfin shad into two Tennessee reservoirs, South Holston and
Watauga, failed due to repeated winter kills (Fetterolf 1956); however, threadfin shad
currently occur in South Holston Reservoir and continue to persist in several other
Tennessee tributary impoundments despite being near the northern limit of their
introduced range (Lee et al. 1980).
In 1976 alewives were stocked into two Tennessee tributary impoundments, Dale
Hollow and Watauga Reservoirs. The objective was to establish a stable forage base for
pelagic piscivores (i.e., walleyes and lake trout Salvelinus namaycush) that was immune
to chronic winter mortalities (D. Peterson, TWRA, personal communication). Alewives
are an anadromous clupeid native to the Atlantic Slope drainage from Labrador to South
Carolina (Lee et al. 1980). Landlocked populations are either the result of canal
construction (e.g., Miller 1957) or intentional introductions. Alewives from Dale Hollow
and Watauga reservoirs originated from Lake Hopatcong, New Jersey (Daniel 1984), the
oldest landlocked population in North America (Gross 1959). Alewife populations have
been stocked in some southern reservoirs because they rarely exceed 200 mm (TL) in
freshwater systems (Rothschild 1966; Daniel 1984) and can withstand water temperatures
below 9οC for extended periods (Otto et al. 1976). Despite possessing numerous
favorable characteristics for a forage fish species, alewives also posses negative
attributes. Alewives are thought to negatively interact with native fish at the larval stage
by competing for food resources (Wells 1970; Hutchinson 1971; Janssen 1976) or by
preying on fish eggs and larvae (Crowder 1980; Kohler and Ney 1980; Brookings et al.
1998). Declines in the abundance of lake herring Coregonus artedii, (Eck and Wells
1987), whitefish C. clupeaformis, (Hoagman 1974), yellow perch Perca flavescens,
(Brandt et al. 1987), and walleye Stizostedion vitreum (Schultz 1992) have coincided
with the establishment of landlocked alewife populations.
Rainbow trout Oncorhyncus mykiss and brown trout Salmo trutta are commonly
introduced in reservoirs of the southeastern United States that have cool, well-oxygenated
water throughout the year to create two-story fisheries. Trout fisheries in southern United
States reservoirs are managed on a put-grow-and-take basis because natural recruitment
does not occur (Jones 1982; Weithman and Haas 1982). Managers can stock different
strains and sizes of trout in lakes and reservoirs to maximize returns to anglers and reduce
18
predation (Babey and Berry 1989; Walters et al. 1997). Fingerling trout have been
stocked in several reservoirs; however, predation by piscivores is often high (Stuber et al.
1985; Yule et al. 2000).
Gizzard shad, threadfin shad and alewives, collectively referred to as clupeids, are
common prey items of walleyes in southern impoundments (Hackney and Holbrook
1978; Daniel 1984). Clupeids accounted for 80% of the identifiable prey of walleyes in
Norris Reservoir, Tennessee (Miranda et al. 1998). Although published accounts of
walleyes foraging on stocked trout in reservoirs of the southeastern United States are
scant, walleyes are known to prey on stocked trout in other reservoirs across North
America (Marwitz and Hubert 1997; Yule et al. 2000).
The objectives of this study were to (1) assess the relative abundance of pelagic
clupeids; (2) describe the size and age structure of six Tennessee walleye populations;
and (3) compare walleye robustness among reservoirs.
METHODS
Collection of Walleyes
Random samples of adult walleyes were collected from six reservoirs in
Tennessee (Table 1) using experimental gill nets (61 m x 2 m; mesh sizes 13, 25, 38, 51,
64 and 76 mm, bar measure) between December and March in the winters of 1998-1999,
1999-2000, and 2000-2001. The number of nets set in each reservoir ranged from 10 to
70 depending on the size of the reservoir; nets were set approximately every 2 river km.
Walleyes were also collected from Center Hill Reservoir in March 1997 with
electrofishing gear. Additional samples of age-1 walleyes in 2000 and 2001 were
collected using 61m x 2 m experimental gill nets comprised of alternating panels of 25
and 38 mm meshes. Gill nets were set at dusk and retrieved the following day. Captured
walleyes were measured (total length, TL; mm), weighed (g) and sexed. Sagittal otoliths
were removed, cleaned and stored in plastic vials. Ages were determined by viewing
cracked or whole-view otoliths under a 10-40x dissecting scope (Erickson 1983). If a
fish was thought to be older than age-1, otoliths were cracked through the focus, polished
with wetted sandpaper and illuminated with a fiber optic light source. Year-class and age
frequency histograms were constructed with data collected in the winters of 1999 and
2000.
Forage Base Assessment
The relative abundance of alewives and threadfin shad was assessed using vertical
gill nets in July and August 1999 in the same reservoirs where walleyes were collected.
Vertical gill nets were constructed of multifilament nylon mesh; each net was 3.7 m X 36
m and sampled the water column from the surface to 36 m. One 13-mm and one 19-mm
mesh net deployed in tandem overnight represented one unit of effort (i.e., net-night).
Three transects were established on each reservoir and were generally located in the
forebay of the dam, mid-reservoir, and below the headwaters. Dale Hollow, Norris,
South Holston, Tellico and Watauga reservoirs each received 10 units of effort and
Center Hill Reservoir received 9 units of effort. At each transect, vertical gill nets were
19
set parallel to shore at dusk and retrieved the following morning. Forty fish of each
clupeid species and mesh size were measured (TL; mm) at each reservoir.
Rainbow trout (> 250 mm, TL) and brown trout (>150 mm, TL) are annually
stocked into Dale Hollow, South Holston, Tellico and Watauga reservoirs and stocking
records from 1995 to 2000 were obtained from the TWRA. Stocking rates for Watauga,
South Holston, Dale Hollow and Tellico reservoirs averaged 17, 13, 7 and 2 trout (both
species combined)/ ha, respectively. Trout have not been stocked into Center Hill and
Norris Reservoirs for at least 20 years.
Data Analysis
Relative stock densities were used to numerically describe the length-frequency
distribution of each walleye population (Anderson and Neumann 1996). Robustness (i.e.,
condition) of walleyes was assessed using two methods: (1) relative weights were
calculated for walleyes using the equation proposed by Murphy et al. (1990), and (2)
annual and spatial variation in walleye robustness was evaluated with analysis-ofcovariance (ANCOVA), using total length as the covariate (Littell et al. 1996). Adjusted
mean weights were compared among reservoirs when the slopes for the log10 length :
log10 weight regressions were similar (P≥0.10). Homogeneity of slopes was achieved by
truncating the range of walleye lengths examined. Annual variation in the adjusted mean
weights of walleyes was also analyzed. Walleyes between 200 and 800 mm TL were
examined in each reservoir, with the exception of Dale Hollow and Norris reservoirs
where the range of lengths examined were 350-800 and 300-800 mm, respectively.
Differences in the adjusted mean weights were determined using pairwise comparisons
(P=0.05). Clupeid catch rates and trout stocking densities were used to explain the
observed variation in adjusted mean weights using linear regression (P=0.10; Neter et al.
1996). Differences in mean size and geometric mean catch of clupeids were tested with
analysis of variance (ANOVA; P=0.05); mean differences were compared with Tukey’s
multiple comparison test (P=0.05).
RESULTS
Forage Base
Geometric mean catches of alewives and threadfin shad (combined) differed
among the six reservoirs (ANOVA, df= 1, 5; F=9.7; P<0.001; Table 2). Alewives were
more abundant in Watauga and Dale Hollow reservoirs, where they were intentionally
stocked in 1976, than in South Holston, Norris, Tellico and Center Hill reservoirs
(ANOVA, df=1,5; F=32.6; P<0.001) where self-sustaining populations arose from illegal
or accidental introductions. Average size of alewives was negatively correlated to catch
rates (r2=-0.75, P=0.08). The largest alewives (>150 mm) were observed where catches
were lowest (e.g., Center Hill and Tellico reservoirs) and alewives were smallest in Dale
Hollow and Watauga reservoirs where catches were high. Threadfin shad were caught in
similar numbers in five of the six reservoirs and ranged in size from 96 to 151 mm; no
threadfin shad were collected from Watauga reservoir (Table 2).
20
Walleye Recruitment and Age-Structure
Natural recruitment of walleyes was hard to detect in Norris, South Holston and
Tellico reservoirs due to annual stockings of walleyes (Appendix A), but appeared to be
minimal in all six reservoirs (Figure 1). Based on the results of marking walleye
fingerlings with oxytetracycline, little to no natural recruitment occurred in Center Hill,
Norris, South Holston and Watauga reservoirs in 1999 and 2000 (see Chapter 1).
Stocking walleyes did not guarantee a strong year-classes in Dale Hollow and Watauga
Reservoirs, but weak or non-existent year-classes occurred during non-stocking years.
Fish belonging to year-classes formed during stocking years also dominated the walleye
populations in South Holston and Center Hill Reservoirs; however, some natural
reproduction was detected in both reservoirs. Walleyes ranged from age-1 to age-21 and
appeared to be fully recruited to the experimental gill nets at age-2 (Figure 2). Although
young fish (< age-5) dominated the catch in all the study reservoirs (Figure 1), older fish
(ages-7 to 16) were collected in Dale Hollow and Watauga reservoirs (Figure 2). The
oldest walleyes were collected from Watauga reservoir; five fish belonged to the 1980
year-class (age-20) and one belonged to the 1979 year-class (age-21).
Condition of Walleyes
Mean relative weights of age-1 walleyes (125-375 mm; TL) ranged between 90
and 104 and were highest in Dale Hollow Reservoir (Figure 3). To achieve homogeneity
of slopes the adjusted mean weights of age-1 walleyes and adult walleyes (i.e., > age-2)
were analyzed separately. Using adjusted mean weights as a measure of robustness, age1 walleyes in South Holston, Center Hill and Norris reservoirs weighed 5-14% less on
average than the same-sized fish in Dale Hollow Reservoir (Table 3). In South Holston,
Dale Hollow and Watauga reservoirs, adult walleyes (375-780 mm) had higher relative
weights (Figure 4) and were more robust (Table 4) than walleyes in Norris, Center Hill,
and Tellico reservoirs. South Holston Reservoir walleyes were more robust than
walleyes from Norris, Center Hill and Tellico Reservoirs (Table 4). Walleyes were most
robust in South Holston Reservoir compared to the other five reservoirs (ANCOVA; df=
6, 1237; F= 1963.3; P<0.001). Walleyes in Center Hill, Dale Hollow, Norris, Tellico and
Watauga Reservoirs weighed between 4 and 16% less than walleyes in South Holston
Reservoir. Adjusted mean weights in each reservoir were not correlated with RSD-P
values (r= 0.40, P=0.42; Figure 5).
Annual variations in walleye robustness were also observed (Table 5). The largest
temporal variation in walleye robustness was observed in Center Hill Reservoir, where
adult walleyes collected in 1998 weighed 9% less than the same-size walleyes collected
in 2000 (ANCOVA, df= 2, 380; F=2789.8; P<0.001). The adjusted mean weight of
walleyes in Dale Hollow Reservoir exhibited a 6% difference in weight between 1997
and 2000 (ANCOVA, df= 2, 211; F=2471.7; P<0.001). Walleyes collected from Norris
Reservoir in 1999 and 2000 weighed 4 and 5% less, respectively, than those collected in
2001 (ANCOVA, df= 3, 591; F= P<0.0003). The difference in the adjusted mean
weights of walleyes collected from South Holston Reservoir in 1999 and 2000 was 4%
(ANCOVA, df= 2, 305; F=4256.5; P<0.001). The adjusted mean weights of walleyes
sampled in the winters of 1998-99 and 1999-00 were similar in Tellico and Watauga
Reservoirs (P>0.40).
21
Variation in the adjusted mean weights of walleyes were not related to the catch
of alewives, threadfin shad, or both species combined (P>0.30). Similarly, adjusted mean
weights were not correlated with trout stocking rates (df=1, 5; F=3.7; r2=0.48; P=0.13);
however, the multiple regression model became significant when threadfin shad catch
rates were entered into the model (df=2, 5; F=5.3; r2=0.78; P=0.10). The explanatory
variables (trout stocking and threadfin shad catch rates) were not correlated (r=-0.52,
P=0.29).
DISCUSSION
The life expectancy of walleyes in the southeastern United States was reported by
Colby et al. (1979) to range between 5 and 7 years of age; however, the presence of old
walleyes (> age-10) in five of the six study reservoirs in the current study contradicts
those findings. The walleyes aged in the studies summarized by Colby et al. (1979) were
most likely aged using scales. Fish aged with otoliths tend to more accurately reflect the
true age of fish (Erickson 1983); therefore, the results of the current study more
accurately reflect the longevity of walleyes in southern impoundments. Although
walleyes as old as age-26 have been reported in Michigan (Schneider et al. 1977) the
presence of older walleyes in Tennessee reservoirs indicated longevity in not necessarily
dependant upon latitude as reported by Colby et al. (1979).
Larval and juvenile walleyes are frequently stocked to supplement natural
recruitment and maintain a fishery (Ellison and Franzin 1992). Natural recruitment of
walleyes in Dale Hollow Reservoir ceased following the introduction of alewives and
year classes formed only during stocked years (Schultz 1992). Similar patterns of
recruitment failure have been observed in Norris and Watauga reservoirs following the
establishment of alewife populations (D. Peterson, TWRA, personal communication) and
are consistent with the patterns of year-class formation observed in this study. In
Horsetooth Reservoir, Colorado, a decline in the recruitment of walleyes was detected
following the introduction of rainbow smelt Osmerus mordax; the decline was attributed
to rainbow smelt piscivory (Jones et al. 1994). Recruitment failure is believed to occur
because alewives and rainbow smelt alter the zooplankton community and prey on larval
fish (Crowder 1980; Kohler and Ney 1980). However, researchers from the New York
Finger Lakes and Great Lakes identified another mechanism that hampers reproduction
by native and introduced salmonids foraging predominately on alewives and rainbow
smelt (Honeyfield et al. 1998). Alewives and rainbow smelt contain thiaminase, a
thiamine-degrading enzyme (Neilands 1947). Thiamine is necessary for normal
neurological function and carbohydrate metabolism in fish (Halver 1989). Salmonids
foraging predominately upon alewives and rainbow smelt exhibited clinical signs of a
thiamine deficiency, which included the inability of sac-fry to survive to the swim up
stage (Fitzsimons and Brown 1988).
The introduction of alewives in Dale Hollow and Watauga Reservoirs succeeded
in establishing a forage base capable of over-wintering, which threadfin shad often can
not accomplish. Landlocked alewives are tolerant of a wide range of temperatures (227οC), but summer and winter die-offs have been observed in some systems (Brown
1972). Widespread winter mortality has not been reported in Tennessee reservoirs (D.
Peterson, TWRA, personal communication).
22
Unlike the populations in Dale Hollow and Watauga Reservoirs, alewife
populations in Center Hill, Norris and South Holston Reservoirs were not established by
the TWRA. Threadfin shad were the only forage fish introduced into Center Hill and
Norris Reservoirs by the TWRA (Fetterolf 1956). In the current study, the catches of
alewives in Center Hill and Norris reservoirs were low (< 25 alewives/ net), but alewife
populations have persisted in both systems (Myhr et al. 1999; Peterson and Negus 1999).
Similar to the establishment of alewives in Lake Ogallala, Nebraska (Porath and Peters
1997), alewives are thought to have migrated downstream into South Holston Reservoir
from Hungry Mother Reservoir, Virginia. Alewives were stocked into Hungry Mother
Reservoir in 1988 to provide forage for walleyes (T. Hampton, Virginia Department of
Game and Inland Fish, personal communication) and were first observed in South
Holston Reservoir in 1993 (Peterson and Negus 1993).
Forage abundance and availability are two factors that influence walleye growth
and condition (Porath and Peters 1997; Jones et al. 1994). In the current study, age-1
walleyes were more robust in reservoirs with high clupeid catch rates and adult walleye
condition (i.e., robustness) was related to trout stocking rates and threadfin shad catch
rates. Walleyes in Dale Hollow Reservoir experienced a significant increase in growth
following the introduction of threadfin shad (Range 1971), similar to the introduction of
rainbow smelt in Horsetooth Reservoir, Colorado (Jones et al. 1994). In two Nebraska
reservoirs, small walleyes were more robust in the reservoir where small prey fish were
abundant (Porath and Peters 1997). In Tennessee reservoirs where walleye condition was
low (e.g., Norris, Center Hill, Tellico), stocking rates should be reconsidered because
competition for food resources is often most intense among members of the same species
(Darwin 1859).
Native salmonids and stocked trout are readily consumed by walleyes
(Beamesderfer and Rieman 1991; Poe et al. 1991; Marwitz and Hubert 1997). Relative
weights of walleyes in two Wyoming reservoirs were positively associated with
fingerling trout stocking densities (Marwitz and Hubert 1997); condition of large
walleyes (> 630 mm, TL) was related to catchable (> 200 mm, TL) and total (i.e.,
fingerling and catchable) trout stocking rates. Large walleyes (> 600 mm) in Dale
Hollow, South Holston and Watauga reservoirs were robust and exhibited high Wr
values, suggesting an adequate forage base was present (Porath and Peters 1997), which
presumably included stocked rainbow trout. Because walleye metabolism increases with
water temperatures (Colby et al. 1979), the presence of a coldwater forage base (e.g.,
stocked trout and alewives) may prevent energy loss and increase fat content (Huh et al.
1976; Serns 1982). However, trout stocking rates alone failed to account for a significant
amount of the variation in the adjusted mean weights of walleyes; only by incorporating
threadfin shad catch rates into the model was a significant amount of the variation in
walleye robustness explained. Miranda et al. (1998) and Smollen (1999) found that
walleyes in Norris Reservoir utilized different prey each season. Alewives were the
dominant forage for walleyes during summer, but shad became more important in the fall
and winter. Similar shifts in diet have been reported for walleyes in Lake Erie (Parsons
1971; Knight et al. 1984). Because shad activity slows as water temperatures decrease
(Strawn 1963), shad are presumably more susceptible than alewives to predation during
the winter months and are also important to the condition of walleyes in southern
impoundments.
23
Table 1. Physical and biological characteristics of six Tennessee reservoirs where walleyes were collected in the winters of 1997-98,
1998-99 and 1999-00. Data for each reservoir was compiled from Myhr et al. (1998a, 1998b), Peterson and Negus (1998a, 1998b)
and Peterson and Thurman (1998a, 1998b).
Year
impounded
Area
(ha)
Mean depth
(m)
Hydraulic
retention time
(d)
Mean annual
fluctuation
(m)
Chlorophyll-a
(mg/ L)
Center Hill
1948
9,224
22
131
9
8.8
Eutrophic
Dale Hollow
1943
12,396
15
343
6
3.5
Mesotrophic
Norris
1936
13,680
18
245
18
2.4
Oligotrophic
South Holston
1950
3,032
27
340
12
4.2
Mesotrophic
Tellico
1980
6,503
8
37
2
6.2
Mesotrophic
Watauga
1948
2,572
27
400
13
4.0
Mesotrophic
Reservoir
1
– Forsberg and Ryding (1980)
24
Trophic State1
Table 2. Geometric mean catch (number of clupeids/ net) and mean total length (mm; TL) of alewives, threadfin shad and combined
catch of both species collected in vertical gill nets from six Tennessee reservoirs, July-August 1999. Means followed by a different
letter within a column were significantly different (Tukey’s comparison; P≤0.05). Confidence intervals (95%) given in parentheses.
Threadfin shad
Alewives
Reservoir
n
Watauga
10
302A
(198, 463)
102E
(1.3)
0B
Dale Hollow
10
207A
(87, 491)
108D
(0.6)
South Holston
10
23B
(13,39)
Norris
10
Tellico
Center Hill
Catch
TL
Catch
Combined
TL
Catch
-
302A
(198,463)
50A
(19,127)
96E
(0.5)
256AB
(97, 559)
126C
(1.3)
62A
(16,234)
112B
(1.4)
116BC
(57,250)
16B
(5,43)
127C
(1.4)
48A
(22,100)
103C
(0.9)
68C
(30,150)
10
8B
(6,10)
180A
(2.6)
25A
(8,75)
151A
(1.2)
42C
(21,77)
9
7B
(4,10)
153B
(1.7)
88A
(46,167)
101D
(0.5)
105C
(60,181)
25
Table 3. Adjusted mean weights of age-1 walleyes collected with gill nets in four
Tennessee reservoirs, during the winters of 1999-2001. Sample size (n) reflects the
number of fish used to calculate the mean weights adjusted to a total length of 270 mm;
adjusted mean weights followed by the same letter were not significantly different
(P>0.05).
Sample
dates
n
Adjusted mean
weight (g)
Percent
difference
Dale Hollow
Dec. 2000
38
187A
0
South Holston
Jan. 2001
79
178B
-5
Center Hill
Jan. 2001
124
172C
-8
Norris
Jan. 1999-01
198
161D
-14
Reservoir
Table 4. Adjusted mean weights of walleyes (375-525 mm) collected with gill nets in six
Tennessee reservoirs, 1997-2001. Sample size (n) reflects the number of fish used to
calculate the mean weights adjusted to a total length of 456 mm; adjusted mean weights
followed by the same letter were not significantly different (P>0.05).
Reservoir
Sample
dates
n
Adjusted mean
weight (g)
Percent
difference
South Holston
Jan. 1999 & 2000
183
1047A
0
Dale Hollow
Dec. 1997 & 20
120
1006B
-4
Watauga
Feb. 1999 & 2000
135
971C
-7
Norris
Jan. 1999-2001
462
930D
-11
Center Hill
Mar. 1998 & Jan. 2000
306
918D
-12
Tellico
Feb. 1999 & 2000
38
879E
-16
26
Table 5. Comparison of adjusted mean weights within a reservoir between years (19972001) for walleyes collected in six Tennessee reservoirs. Sample size (n) reflects the
number of fish used to calculate the adjusted mean weights. Adjusted mean weights
within a reservoir followed by the same letter were not significantly different (P>0.05).
Year
n
Adjusted
mean length
(mm)
Center Hill
2000
1998
229
154
470
1038A
944B
0
-9
Dale Hollow
2000
1997
163
51
512
1419A
1338B
0
-6
2001
1999
2000
213
76
306
462
973A
935B
926B
0
-4
-5
South Holston
2000
1999
220
88
508
1497A
1433B
0
-4
Tellico
2000
1999
19
59
537
1462A
1461A
0
< -1
Watauga
1999
2000
155
49
475
1078A
1068A
0
-1
Reservoir
Norris
27
Adjusted
mean weight
(g)
Percent
difference
80
1999
Tellico
n=144
Frequency
40
(1)
0
1977
Watauga1980
1983
1986
1989
1992
1995
1998
1992
1995
1998
1993
1996
1999
1993
1996
1999
1993
1996
1999
1993
1996
1999
n=158
40
0
160
(1)
(1)
1977
1980
1983
Center Hill
n=226
(1)
1986
1989
2000
80
0
(1)
1978
1981
Dale Hollow
1984
1987
1990
Frequency
n=200
40
0
(1)
1978
Norris 1981
1984
1987
1990
n=305
80
0
(1)
(1) (1)
1978
1981
South Holston
1984
1987
1990
n=211
40
0
(1)
1978
1981
1984
1987
1990
Year-Class
Figure 1. Year-class frequencies of walleyes collected in six Tennessee
reservoirs with experimental gill-nets in the winters of 1998-99 (top panels) and
1999-2000 (bottom pannels). Black columns represent years that walleyes were
stocked and white columns indicate non-stocking years. Number of fish belonging
to a given year-class in parentheses.
28
600
500
n=1,763
Frequency
400
300
200
100
(3)
0
1
3
5
7
9
11
13
(2)
(1)
15
17
19
21
23
Age (years)
Figure 2. Age-frequency distribution of walleyes collected from six Tennessee
reservoirs with experimental gill-nets in the winters of 1998, 1998-99,1999-00 and
2000-01. Number of fish collected shown in parentheses for the older age-classes.
29
140
Dale Hollow
Mean Wr=104
120
100
80
60
140100
120
150
200
250
300
350
400
200
250
300
350
400
200
250
300
350
400
200
250
300
350
400
South Holston
Mean Wr=98
Relative Weight
100
80
60
140100
150
Center Hill
Mean Wr=96
120
100
80
60
100
140
120
100
150
Norris
Mean Wr=90
80
60
100
150
Total Length (mm)
Figure 3. Relative weights (Wr) of age-1 walleyes collected in the winters of 1999,
2000 and 2001. Dashed line represents a Wr value of 100.
30
140
120
100
South Holston
Mean Wr=107
80
60
140300
400
500
600
700
800
120
100
Dale Hollow
Mean Wr=99
80
60
300
140
400
500
600
700
800
120
Relative Weight
100
Watauga
Mean Wr=98
80
60
140300
400
500
600
700
800
120
100
Norris
Mean Wr=94
80
60
140300
400
500
600
700
800
120
100
Center Hill
Mean Wr=93
80
60
140300
400
500
600
700
800
Tellico
Mean Wr=90
120
100
80
60
300
400
500
600
700
Total Length (mm)
Figure 4. Relative weights of age-2 and older walleyes collected in the winters of
1997, 1998-99 and 1999 2000 from six Tennessee reservoirs. Dashed line
represents a Wr value of 100.
31
800
80
Tellico
RSD-P=53
n=170
1999
40
0 200
275
350
425
500
575
650
1999
200
275
350
425
500
575
650
Frequency
2000
200
275
350
425
500
575
650
40
40
275
350
425
500
575
650
350
425
500
575
650
350
425
500
575
650
2000
0 200
275
2000
40
0 200
800
275
725
800
Dale Hollow
RSD-P=58
n=200
2000
0 200
725
Center Hill
RSD-P=17
n=229
40
0
800
Watauga
RSD-P=32
n=160
40
0
725
725
800
725
800
725
800
Norris
RSD-P=17
n=331
South Holston
RSD-P=53
n=222
Total Length (mm)
Figure 5. Length frequencies and relative stock density of walleyes larger than
510 mm (RSD-P; Anderson and Neumann (1996)) collected from six Tennessee
reservoirs in the winters of 1999 and 2000. Dashed lines represent the 381 mm
minimum size limit in Norris, South Holston, Tellico and Watauga reservoirs and a
406-mm minimum size limit in Center Hill and Dale Hollow reservoirs.
32
CHAPTER III
EVALUATION OF THE CURRENT MINIMUM SIZE LIMITS
FOR WALLEYES IN TENNESSEE
ABSTRACT
Walleye yield in six Tennessee reservoirs was simulated with an equilibrium yield
model under different size limit scenarios: no-limit (i.e., 253 mm), the current minimum
size limit in each reservoir (381 or 406 mm) and a 457-mm minimum size limit. All
simulations were run with conditional natural mortality rates (cm) of 0.10, 0.20 and 0.30
and conditional fishing mortality rates between 0.20 and 0.50. All minimum size limits
increased yield in all reservoir compared to no size limit at most levels of exploitation
when cm rates were low (< 20%). At higher natural mortality rates, the benefits of any of
the minimum size limits were eliminated. The longevity of walleyes (maximum age
averaged 13 years) indicated that natural mortality rates were low; thus, minimum size
limits were appropriate management actions in all reservoirs. Although yield was usually
highest under a simulated 457-mm length limit, the benefits were slight unless
conditional fishing mortality rates were high (> 40%) and natural mortality rates were
low (10%).
INTRODUCTION
Prior to the construction of hydroelectric dams on the Cumberland and Tennessee
rivers, seasonal walleye Stizostedion vitreum fisheries occurred in the Caney Fork,
Clinch, Powell and Obey rivers. Following impoundment, walleyes harvested by anglers
and collected during fish inventories were large, up to 9 kg (Fetterolf 1954; Netsch and
Turner 1964). However, native walleye populations were unable to sustain themselves
and progeny from Great Lakes walleye stocks were subsequently introduced to reestablish self-sustaining populations (Fetterolf 1956). Southern stocks of walleyes were
obligate river spawners that had specific spawning requirements which were not met after
impoundment (Hackney and Holbrook 1978). Information concerning harvest
restrictions on Tennessee reservoirs following impoundment is scant, but season closures
occurred on some reservoirs such as on Norris Reservoir, where Eschmeyer (1944)
concluded that walleyes were under-exploited and restrictive regulations should be
removed. Fitz and Holbrook (1978) thought that exploitation was low and natural
mortality was high for walleyes and saugers S. canadense in Norris Reservoir because
few old fish (i.e., older than age-3) were collected. Additionally, they concluded that
exploitation rates were similar to those reported by Eschmeyer (1944). In a review of
walleye populations across North America, Ney (1978) and Colby et al. (1979) reported
that annual mortality for walleyes ranged between 5 and 50% and that exploitation was
between 5 and 47%.
Restrictive harvest regulations are imposed on commercial and recreational
fisheries to meet specific management goals for biological, ecological, and
socioeconomic reasons (Noble and Jones 1993). Numerous types of restrictive
regulations exist, but the most common restrictions are based on the size and number
33
(creel) of fish to be harvested. Size and creel regulations are imposed on walleye
fisheries across North America (e.g., Johnson et al. 1992; Munger and Kraai 1997) to
maintain satisfactory exploitation rates and allocate the resource among participants;
however, management objectives may not be met if the incorrect size or creel limits are
imposed. Since few anglers actually harvest their limit, creel limits alone are usually
ineffective in preventing overexploitation (Quinn 1992; Noble and Jones 1993; Munger
and Kraai 1997); thus, creel limits in conjunction with size limits are commonly used to
manage recreational fisheries. Walleye populations have been managed with three types
of size restrictions (1) minimum length, (2) maximum length and (3) slot limits, each
designed to protect and enhance the fishery differently (Brousseau and Armstrong 1987).
Minimum lengths are commonly tailored to lakes and reservoirs that exhibit
similar growth and mortality rates, ensuring that fish spawn at least once during their life.
Conversely, maximum size limits protect fish over a certain size and allow smaller fish to
be harvested. Maximum size limits serve to protect broodstock when exploitation is high
and natural recruitment and the abundance of sexually mature fish is low. However,
angler non-compliance may negate any potential benefits of a maximum size limit if
anglers are unwilling to release large fish (Gigliotti and Taylor 1990). Slot limits protect
fish within a specified length range (i.e., the “slot”) and enable anglers to harvest fish
outside the slot. Slot limits are used when recruitment is high and natural mortality is
low. The potential beneficial aspects of a slot limit may also be undermined by angler
non-compliance.
In 1997 the Tennessee Wildlife Resources Agency (TWRA) enacted a 406-mm
total length (TL) minimum size limit for most walleye fisheries to reduce exploitation
and distribute the resource among anglers (T. Churchill, TWRA, personal
communication). The minimum size limit for walleyes in Norris, South Holston, Tellico
and Watauga reservoirs was set at 381-mm, TL. The efficacy of imposing restrictive
harvest regulations on walleyes has not been thoroughly evaluated in Tennessee; thus, the
primary objective of this study was to simulate yield of six Tennessee walleye
populations under different management scenarios: no size-limit, current minimum size
limits (381-mm or 406-mm) and a hypothetical 457-mm minimum size limit.
METHODS
Fish Collections and Growth Analyses
Walleyes were collected in the winters of 1997-98, 1998-99, and 1999-00 from
six Tennessee reservoirs (Table 1) with experimental gill nets (61 m x 2 m; mesh sizes
13, 25, 38, 51, 64 and 76 mm, bar measure) and electrofishing gear. Captured walleyes
were weighed (g), measured (TL; mm) and sexed; sagittal otoliths were extracted for age
determination (Erickson 1983). Ages were determined by viewing whole view or
cracked otoliths under a 10-40 X dissecting scope. Otoliths from fish older than age-1
were cracked along the transverse axis of the nucleus, polished with fine sandpaper and
viewed using a fiber-optic wand (Heidinger and Clodfelter 1987). Relative stock
densities were used to numerically describe the length-frequency distribution of each
walleye population (Anderson and Neumann 1996). Growth was described using the von
Bertalanffy (1938) growth model; the parameters of the model were estimated using
Fisheries Analysis and Simulation Tools (FAST) software (Slipke and Maceina 2000).
34
For age-classes with at least three fish, mean length-at-age was determined and the
parameters K, t0 and L∞ were calculated for each reservoir, where K is the Brody growth
coefficient, t0 is the time in years when length would theoretically be equal to zero and L∞
is the theoretical maximum length if the fish was to live and grow indefinitely (Ricker
1975). The von Bertalanffy growth model was used to estimate when (T, in years) fish
would enter the fishery under the current size limits (T381 mm or T406 mm) and a hypothetical
457-mm size limit (T457 mm).
Simulated Yield
Walleye yield was simulated in FAST using the Jones (1957) modification of the
Beverton-Holt (1957) equilibrium yield model, as described by Ricker (1975).
Parameters of the log10length:log10weight regression model (i.e., slope [a’]and yintercept, [b]) and the von Bertalanffy growth model (K, t0 and L∞) were entered into the
yield model and simulations were run with 100 recruits entering the fishery at time zero.
Yield was modeled assuming that a Type II fishery existed (i.e., natural and fishing
mortality rates were additive and occurred simultaneously; Ricker 1975). Simulations in
FAST were run using conditional fishing mortality rates (cf) of 0.20, 0.30, 0.40 and 0.50
based on reported estimates of exploitation (u) for walleyes in Tennessee and Virginia
reservoirs (Table 2). The other measure of mortality needed to simulate yield is
conditional natural mortality (cm), which can be determined if u and total annual
mortality are known. Total annual mortality (AM) equals the number of deaths caused
by natural causes (v) and fishing (u) within a year and can be estimated by fitting a catch
curve to number-at-age data (Ricker 1975). Similar to the relationship between u and cf,
cm is analogous to v (Ricker 1975); thus, cm can be determined if AM and u are known.
Catch curves can be used to estimate AM (and cf and cm if u or v are known), but certain
assumptions must be met, specifically: (1) recruitment is constant, (2) survival is similar
among year classes and survival is constant from year to year, and (3) catch curves are
fitted to data that reflect the true age structure of the population (Ricker 1975). Natural
recruitment was limited in Dale Hollow, Norris, South Holston, Tellico and Watauga
reservoirs (see Chapter 1) and walleye fingerlings were stocked at various rates to sustain
these fisheries; thus, the assumption of equal recruitment in each fishery was violated and
catch curves could not be used to determine mortality. Catch curve analysis was used to
estimate AM in Center Hill Reservoir where the fishery has been sustained via natural
recruitment since the 1960’s; however, cm could not be estimated because u is unknown.
Weighted linear regression was used to estimate AM because few old fish were collected
during 1998 and 1999-00 (Slipke and Maceina 2000). Natural mortality rates are
unknown for Tennessee walleye populations; therefore, cm was determined by first
estimating the instantaneous natural mortality rate (M) using the methods of Quinn and
Deriso (1999):
M = -ln (Ps) / tmax
(equation 1),
where tmax is the maximum age in a population and Ps is the proportion of the population
that survives to tmax. Shepard and Breen (1992) suggested that 5% is a reasonable
35
estimate of Ps and the mean tmax for walleye populations in the six study reservoirs was
13 years; thus, M = 0.23 using equation 1. The relation between M and cm is as follows:
cm = 1 – e –M
(equation 2);
thus, cm = 0.21 when M = 0.23.
This approximate cm rate (0.21) was bracketed by 0.10 and yield was subsequently
simulated at cm rates of 0.10, 0.20 and 0.30 to reflect scenarios of low, moderate and
high levels of natural mortality, respectively. Yield was modeled assuming no size-limit
(i.e., 253 mm, TL), the current size limit (i.e., either a 381- or 406-mm size limit) and a
457-mm size limit regulation. The simulated change in yield (i.e., % difference) was
calculated to estimate the expected increase in yield under the different minimum size
limits (i.e., a 381, 406- or 457-mm size limit).
RESULTS
Size and Age Structure
Length-frequency distributions revealed that walleyes were not stockpiling below
the 381-mm or 406-mm size limits in any of the study reservoirs (Figure 1). Walleyes
less than 375 mm were predominately age-1 fish stocked the previous spring. According
to the von Bertalanffy growth models, maximum asymptotic lengths (L∞) were higher (>
600 mm) in Dale Hollow, Tellico and Watauga reservoirs than in Center Hill, Norris and
South Holston reservoirs (L∞ < 564 mm; Figure 2). Mean asymptotic lengths were
inversely related (df=1,4; F=20.5; r2=0.84; P=0.01) to K, the Brody growth coefficients
(r=0.92; P=0.01; Table 3). Under current size limits, walleyes recruited to their
respective fisheries between 1.5 and 2.1 years of age. Most (92%) walleyes collected
during the study were young (< age-7; Figure 3); however, numerous old walleyes (age10 through 16) were collected in Dale Hollow and Watauga reservoirs and the oldest
walleye collected was an age-21 individual from Watauga Reservoir (Figure 4). Total
annual mortality for Center Hill Reservoir walleyes collected in 1998 and 1999-00 was
46 and 60%, respectively (Figure 5). Those mortality estimates applied to walleyes
between age-2 and age-9.
Minimum Size Limit Evaluation
The parameters used to model yield with three different management regulations
are presented in Table 3. Minimum size limits failed to increase yield over all ranges of
exploitation (u) when conditional natural mortality (cm) was 0.30. When natural
mortality was lower (cm=0.10 or 0.20), minimum size limits increased yield in each
reservoir (Figures 6-11). Compared to a no-limit regulation, yield increased 14-20% with
size limits in each reservoir at a cm of 0.20 when u exceeded 20%, but there was little (<
4%) difference in yield between the different minimum size limits. Size limits would
increase yield the greatest (17-26%) over all ranges of exploitation if cm was 0.10 in each
of the six study reservoirs. The increase in yield would be most pronounced (25-26%)
36
for the walleye populations in Dale Hollow, Tellico and Watauga reservoirs (Figures 7,
10 and 11) where the lowest values of K and the greatest maximum lengths (L∞) were
observed. However, the predicted number of fish harvested would decrease 6-12% by
imposing a minimum size limit (Figure 12). Imposing a minimum size limit of 457-mm
would maximize yield in each reservoir (Figures 6-11) and the difference in yield would
be between 5 and 13%, but the number of fish harvested would decrease by 6-11%
(Figure 12). Only marginal benefits (i.e., < 6% difference in yield) would be expected by
increasing the current minimum size limit (381-mm) for walleyes in Norris, South
Holston, Tellico and Watauga reservoirs to the statewide minimum size regulation (i.e.,
406-mm; Figures 8-11).
DISCUSSION
Despite different growth rates and size and age structures, walleyes in the study
reservoirs responded to minimum size limits in a similar manner when natural mortality
was high (cm=0.30). Maceina et al. (1998) found the same to be true for saugers in the
lower portion of the Tennessee River; simulated yields were low at a high rate of cm and
at all levels of cm a minimum size limit increased yield. For Tennessee walleyes, harvest
regulations did not increase yield when cm was high, similar to observations for black
basses Micropterus spp. (Austen and Orth 1988). When fish die of natural causes at a
high rate, a minimum size limit does not increase yield because too many fish die before
reaching the size limit.
Benefits of restrictive regulations were evident for walleyes in Tennessee
reservoirs when natural mortality was assumed to be at low or moderate levels (cm ≤
0.20). At these levels of cm, growth over fishing would occur if no limit were in place
because numerous walleyes would be harvested prior to reaching their full growth
potential. Current size limits or a 457-mm minimum size limit on each of the study
reservoirs would prevent this from occurring. Saugers in the Tennessee River were also
susceptible to growth over fishing and Maceina et al. (1998) predicted yield would
increase with the enactment of a minimum size limit. Allen and Miranda (1995) reported
that a minimum size limit for crappies Pomoxis spp. would not be beneficial regardless of
growth rates unless cm was low (<0.30).
Estimates of annual mortality for walleyes in Center Hill Reservoir (46 and 60%)
were within the range of mortality rates for adult walleyes in North America (13-80%)
reported by Colby et al. (1979). Based on size and age class distributions, annual
mortality of walleyes in Tennessee was likely system-specific. In Dale Hollow and
Watauga Reservoirs, walleyes attained large sizes and age frequencies indicated that
annual mortality was low because walleyes were long-lived (Tmax >13 years).
Conversely, the size structure of walleyes from Center Hill and Norris reservoirs (i.e.,
low RSD-P values) indicated high levels of annual mortality. Age frequency
distributions also suggested that annual mortality was high for walleyes in Center Hill
Reservoir, where only one fish older than age-4 was collected. Muench (1966) and Scott
(1976) collected numerous large walleyes (range: 607-722 mm, TL) in Center Hill
Reservoir; however, in the current study only one fish larger than 600 mm was observed,
suggesting that Center Hill Reservoir has the potential of producing large walleyes, but
fish are removed by anglers before they attain large sizes. Twenty-five years ago, Scott
37
(1976) characterized Center Hill Reservoir as one of the premier walleye fisheries in
Tennessee. In 2000, 33% of intended effort for walleyes in Tennessee occurred on
Center Hill Reservoir (Malvestudo and Black 2001), indicating that this reservoir
continues to be regarded as a popular walleye fishery.
The walleye stocking program in Norris Reservoir has intensified since 1997
(Peterson and Negus 1999); consequently, the ability to model this fishery under different
harvest regulations was difficult because the age and size distributions were skewed
towards young, small individuals. It would appear that annual mortality was low because
old walleyes (up to age-11) were present; however, walleyes did not attain large sizes.
Stroud (1949) noted that most walleyes in Norris Reservoir were between 300 and 500
mm TL, with few fish larger than 600 mm, similar to the findings of the current study.
Norris Reservoir was also considered to be a popular walleye fishery based on the 2000
TWRA statewide creel survey, where 27% of the intended angler effort was directed
toward walleyes (Malvestuto and Black 2001). Thus, the role that exploitation plays in
determining the size structure of walleyes in Center Hill and Norris Reservoirs must also
be considered before imposing a 457-mm size limit.
In Meredith Reservoir, Texas, the establishment of a 407-mm minimum size limit
caused a decline in growth for walleyes less than age-5, but the age at which walleyes
reached legal size remained unchanged and the abundance of legal-sized fish increased
(Munger and Kraai 1997). Schneider (1978) used the Ricker Equilibrium Yield Model to
predict the response of changing the minimum size limit for walleyes from 330 mm to
381 mm in a Michigan walleye fishery. The regulation was predicted to cause little
change in yield, an increase in the total number of legal and sub-legal walleyes caught,
and a 10-25% decrease in the number of legal-sized walleyes harvested. Serns (1978)
reported that walleyes in a Wisconsin lake stockpiled below the minimum size limit and
catch and yield decreased four-fold following the enactment of a 381-mm minimum size
limit. Serns (1978) further concluded that minimum size limits would be most
appropriate for walleye populations with limited natural reproduction, good growth, low
natural mortality and high exploitation.
The rate at which walleyes die of natural causes will determine the appropriate
harvest regulation for walleyes in Tennessee reservoirs. The results of this study support
the findings of Brousseau and Armstrong (1987) that statewide harvest regulations may
not be appropriate due to varying rates of growth and mortality and that harvest
regulations should be system-specific. Future studies should focus on determining total
annual mortality rates and the rate at which walleyes die of natural causes. The walleye
telemetry (Schultz 1992) and tagging (Peterson and Lane 1989) studies in Dale Hollow
and Norris reservoirs, in addition to the studies done with walleyes in a Virginia
reservoir (Palmer 1999), provide an estimate of exploitation for walleyes in southern
impoundments. Similarly, Hightower et al. (2001) used telemetry to estimate natural and
fishing mortality for striped bass Morone saxatilis in a North Carolina river-system.
Although catch-curve analysis cannot be used to estimate annual mortality for most
Tennessee walleye populations, mortality can be estimated by following an individual
year-class through time (Ricker 1975). The rate at which walleyes die of natural causes
can then be determined because estimates of exploitation exist for several fisheries. This
information would provide TWRA fisheries managers with the information needed to
accurately simulate walleye yield in Tennessee reservoirs and determine the size limit
38
that would maximize yield in each reservoir. Although simulated yields were often
maximized with high minimum size limits, the number of fish annually harvested
decreased; thus, angler motivations are an important consideration when setting
restrictive regulations (Spencer 1993) and should be incorporated into the management
process for Tennessee walleye fisheries.
39
Table 1. Physical and biological characteristics of six Tennessee reservoirs where walleyes were collected in the winters of 1997-98,
1998-99, 1999-00; hydraulic retention time (HRT) and mean annual water level fluctuation (MAF). Data for each reservoir were
compiled from Myhr et al. (1998a, 1998b), Peterson and Negus (1998a, 1998b) and Peterson and Thurman (1998a, 1998b).
Year
impounded
Area
(ha)
Mean depth
(m)
HRT
(d)
MAF
(m)
Chlorophyll-a
(mg/ L)
Center Hill
1948
9,224
22
131
9
8.8
Eutrophic
Dale Hollow
1943
12,396
15
343
6
3.5
Mesotrophic
Norris
1936
13,680
18
245
18
2.4
Oligotrophic
South Holston
1950
3,032
27
340
12
4.2
Mesotrophic
Tellico
1980
6,503
8
37
2
6.2
Mesotrophic
Watauga
1948
2,572
27
400
13
4.0
Mesotrophic
Reservoir
1
– Forsberg and Ryding (1980)
40
Trophic State1
Table 2. Reported exploitation rates for walleyes in Tennessee and Virginia. Type of study (TAG= reward tags, TEL= telemetry
tags) indicates how exploitation was determined. Exploitation rates followed by an asterisk (*) were corrected for tag loss and nonreporting biases.
Location
Area
Type of
Study
Study period
Rate of
Exploitation (%)
Citation
Tennessee
Dale Hollow Reservoir
12,396
1990-91
TEL
30
Schultz (1992)
Norris Reservoir
13,680
1989-90
TAG
31*
Peterson and Lane (1989)
Norris Reservoir
13,680
1990-91
TAG
18*
Peterson (1990)
Norris Reservoir
13,680
1994-95
TAG
30*
O’Bara (1999)
Norris Reservoir
13,680
1997-98
TAG
15*
O’Bara (1999)
1,820
1997-99
TEL
19
Palmer (1999)
Hungry Mother Reservoir
44
1997-98
TAG
32
Hampton (1998)
Hungry Mother Reservoir
44
1998-99
TEL
33
Hampton (1999)
Lake Whitehurst
202
1997-98
TAG
40
Eades (1998)
Lake Whitehurst
202
1998-99
TEL
44
Eades (1999)
Virginia
Claytor Lake
41
Table 3. Parameters used to simulate walleye yield in six Tennessee reservoirs using Fishery Analysis and Simulation Tools software
(FAST; Slipke and Maceina 2000). Slope (b) and intercept (a’) were derived from the log10length:log10weight relationship for each
reservoir. Sample size (n) reflects the number of walleyes used to calculate asymptotic maximum total length (L∞ ), Brody growth
coefficient (K), time when total length is 0 (t0) and time to reach a 381, 406 and 457-mm minimum size limit (Tr 381, 406 and 457 mm) using
the von Bertalanffy growth model.
K
t0
Tr 381 mm
Tr 406 mm
Tr 457mm
549
0.79
0.07
n/a
1.8
2.3
3.08
600
0.48
-0.45
n/a
1.9
2.5
-5.30
3.11
544
0.69
-0.08
1.7
1.9
2.5
312
-5.94
3.34
564
0.84
0.19
1.5
1.7
2.2
Tellico
162
-5.64
3.23
616
0.35
-1.14
1.6
1.9
2.7
Watauga
190
-5.40
3.16
615
0.36
-0.87
1.8
2.1
2.9
Reservoir
n
a’
b
Center Hill
509
-5.31
3.11
Dale Hollow
197
-5.17
Norris
392
South Holston
L∞
42
43
44
600
500
n=1,763
Frequency
400
300
200
100
(3)
0
1
3
5
7
9
11
13
(2)
(1)
15
17
19
21
Age (years)
Figure 3. Age-frequency distribution of walleyes collected from six Tennessee
reservoirs with experimental gill-nets in the winters of 1998, 1998-99,1999-00 and
2000-01. Number of fish collected shown in parentheses for the older
age-classes.
45
23
46
6
1998
Z= -0.62
A= 0.46
r2= 0.74
Natural logarithm of catch
4
2
0
0
2
4
6
8
10
6
2000
Z= -0.91
A= 0.60
r2= 0.77
4
2
0
0
2
4
6
8
10
Age (years)
Figure 5. Catch curves for walleyes collected from Center Hill Reservoir with
electrofishing gear in March 1998 and experimental gill nets in the winter of
1999-00 (2000). Mortality was determined using weighted regression.
47
48
49
50
51
52
53
54
CHAPTER IV
MANAGEMENT IMPLICATIONS
Efficacy of Stocking Walleyes to Augment Recruitment
Tennessee fisheries biologists have long relied on stocking walleye fry or
fingerlings to supplement natural recruitment in many reservoirs, or provide offspring
where none were produced by wild fish. Our findings indicate that most walleye fisheries
in Tennessee will need to rely on a stocking program to remain viable. Although the exact
mechanism responsible for walleye recruitment failure in recent decades is unknown, the
establishment of alewife populations has invariably preceded recruitment failure. Even
fisheries that were self-supporting for many decades, such as those in Norris and Center
Hill Reservoirs, are in jeopardy because alewives appeared in each system in the 1990’s
and recent year classes were comprised almost entirely of stocked walleyes. Alewives
were recently observed in Tims Ford Reservoir (J. Riddle, TWRA, personal observation);
thus, alewives are now found in every Tennessee reservoir that supports a walleye fishery.
Biologists can confirm (or refute) the observation that natural walleye recruitment has
ceased in Norris and Center Hill Reservoirs by continuing to stock (and recapture) OTCmarked fingerlings for several more years. Continuing the OTC-marking program should
enable TWRA biologists to determine how different hydrologic conditions (i.e., dry and
wet years) influence the contribution of stocked fish to the fishery.
Forage Abundance and Stocking Rates
With increased reliance on stocking programs to maintain individual fisheries,
hatchery-reared fingerling walleyes will become a limited resource. Even if hatchery
operations are upgraded and expanded, it will be important to wisely allocate hatchery
fingerlings to maximize benefits to anglers. Ideally, stocking rates should be matched to
forage abundance in each reservoir, but such information is expensive to obtain. Instead,
indirect measures of forage availability could be obtained, such as:
(1) Measuring catch-per-unit-effort of clupeids in experimental gill nets. If
sampling was conducted in summer (during stratification), vertical gill nets with different
mesh sizes (at least two, preferably more mesh sizes) could be deployed to sample the
clupeid forage base. Horizontal nets with varying meshes (see VanDenAvyle et al. 1995)
could also be used to sample those populations, but only during the spring spawning
season when alewives and threadfin shad move inshore to spawn in shallow water.
(2) Measuring walleye robustness and growth rates. Forage availability
will influence walleye growth rates and robustness. Populations of individuals with low
condition values (i.e., low Wr’s) should prompt biologists to consider stocking fewer
walleyes. Most sport fish in Tennessee reservoirs feed on clupeids, but competition for
those resources is likely to be most intense among individuals of the same species.
55
Examining Wr’s and growth rates of the principal sport fish species in each reservoir might
shed additional light on forage availability and stocking rates.
Walleye stocking rates in Tennessee tend to be based on historical precedents and
hatchery production constraints rather than the characteristics of the receiving waters.
Stocking rates throughout Tennessee need to be revisited because we detected statistically
and biologically significant differences in clupeid abundance and walleye robustness
among the six study reservoirs. Future walleye stockings could be treated as experiments
by varying the rates and following individual year classes through time. For instance, if
reducing the walleye stocking rate in Norris Reservoir for several years improves the
robustness of adults and does not appreciably reduce catch rates, than more fish could be
allocated to systems that can probably sustain higher stocking rates (e.g, Dale Hollow,
South Holston, and Watauga).
The importance of stocked trout as forage for walleyes in several reservoirs
(notably Watauga and South Holston) was suggested by statistical models and the
literature. Our own observations that walleyes were preying on trout indicated that trout
were an important diet item. A thorough examination of walleye diets would provide
valuable information to biologists tasked with managing walleyes and trout in those three
reservoirs.
Effects of Minimum Size Limits on Yields
Given what we know about natural mortality rates and exploitation rates, minimum
size limits in Tennessee are appropriate management tools for preventing growth
overfishing and increasing yields. The differences between minimum size limits currently
in effect (381 mm and 406 mm ) and a hypothetical minimum size limit (457 mm) were
too subtle to warrant any changes in current regulations given our imperfect knowledge of
exploitation and natural mortality rates. If TWRA biologists want to “fine-tune” their
walleye regulations, they will need to generate estimates of total mortality using techniques
other than linear catch-curve analysis (e.g., following individual cohorts through time).
Current estimates of exploitation for several populations, using identical methodologies,
would also be highly desirable. Any proposed changes should also be preceded by a
survey of anglers to determine the support for a new regulation intended to change the
average size and number of fish they harvested.
The Future of Walleye Fishing in Tennessee
Annual yield (kg/ha) of Tennessee’s principal walleye fisheries ranked only as
“fair-to-good” when compared to other walleye fisheries throughout North America.
However, walleyes in Tennessee grow very fast, display good longevity, and can achieve
excellent Wr’s compared to populations elsewhere. In these respects, several Tennessee
populations (Dale Hollow, South Holston, Watauga) would be considered excellent
fisheries elsewhere in North America. The yields that Tennessee reservoirs produce are
ultimately a function of walleye population size, which is probably influenced in most
instances by stocking rates. Thus, biologists may have the opportunity to directly affect
fishery yields by altering stocking rates. If the biomass of walleyes appears to be below a
56
system’s carrying capacity (based on Wr’s), higher stocking rates might increase the yield
and quality of the fishery.
57
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APPENDICES
69
Appendix A. Number, size, density (#/ ha), source of broodfish (CH = Center Hill, DH = Dale Hollow, GL = Great Lakes, GF = Greers Ferry, KS = Kansas
Broodfish, KY = Kentucky, N = Norris, WI Wisconsin, VA = Virginia) and year when walleyes were stocked into Center Hill, Dale Hollow, Norris, South
Holston, Tellico and Watauga reservoirs since impoundment.
Year
Number Stocked
Size
Density
Source
Citation
1,500,000
1,500,000
750,000
2,900,000
1,313,693
695,457
195,328
fry
fry
fry
fry
fry
fry
fingerling
163
163
81
.
142
75
21
GL
GL
GL
GL
CH, DH
CH
CH
Fetterolf (1956); Muench (1966)
Fetterolf (1956); Muench (1966)
Fetterolf (1956); Muench (1966)
Muench (1966)
T. Churchill, TWRA, unpublished data
T. Churchill, TWRA, unpublished data
T. Churchill, TWRA, unpublished data
1,500,000
1,000,000
750,000
1,635,750
150,000
2,000,000
4,500,000
391,120
180,059
302,801
200,000
331,791
235,292
333,160
273,139
201,978
fry
fry
fry
fry
fry
fry
fry
fingerling
fingerling
fingerling
fry
fingerling
fingerling
fingerling
fingerling
fingerling
121
81
61
132
12
161
363
32
15
24
16
27
19
27
22
16
GL
GL
GL
GL
GL
GL
GL
DH, KY
DH
DH, GF
DH
GF, KY
DH
DH
DH, CH
DH, CH
Fetterolf (1956); Libbey (1969)
Fetterolf (1956); Libbey (1969)
Fetterolf (1956); Libbey (1969)
Libbey (1969)
Libbey (1969)
Libbey (1969)
Libbey (1969)
Myhr et al. (1998)
Myhr et al. (1998)
Myhr et al. (1998)
Myhr et al. (1998)
Myhr et al. (1998)
Myhr et al. (1998)
Myhr et al. (1998)
Myhr et al. (1998)
Myhr et al. (1999)
Center Hill
1954
1955
1956
1957-60
1996
1998
2000
Dale Hollow
1954
1955
1956
1957
1958
1961
1965
1987
1988
1990
1990
1991
1993
1995
1997
1999
70
Appendix A. (Continued)
Year
Number Stocked
Size
Density
Source
Citation
Norris
1992
1993
1994
1995
1996
1997
1998
1999
2000
32,317
35,052
87,679
5,000
630,000
135,707
414,762
334,878
347,465
fingerling
fingerling
fingerling
fingerling
fry
fingerling
fingerling
fingerling
fingerling
2
3
6
<1
46
10
30
24
25
N
N
N
GF
N, GF
N
N, KY
N, KY
N, KY
Peterson and Negus (1993a)
Peterson and Negus (1996)
Peterson and Negus (1994a)
Peterson and Negus (1995a)
Peterson and Negus (1996)
Peterson and Negus (1997)
Peterson and Negus (1998a)
Peterson and Negus (1999a)
Peterson and Negus (2000a)
35,000
25,457
52,752
33,730
27,300
29,656
30,000
0
31,900
0
37,900
39,182
39,508
146,360
fingerling
fingerling
fingerling
fingerling
fingerling
fingerling
fingerling
12
8
17
11
9
10
10
VA
VA
VA
VA
VA
VA
VA
fingerling
11
VA
fingerling
fingerling
fingerling
fingerling
13
13
13
48
N
VA
N
VA
T. Churchill, TWRA, unpublished data
T. Churchill, TWRA, unpublished data
T. Churchill, TWRA, unpublished data
Peterson and Lane (1989a)
T. Churchill, TWRA, unpublished data
T. Churchill, TWRA, unpublished data
Peterson and Negus (1993b)
Peterson and Thurman (1997)
Peterson and Thurman (1995)
Peterson and Thurman (1997)
Peterson and Thurman (1998a)
Peterson and Thurman (1998a)
Peterson and Thurman (1999a)
Peterson and Thurman (2000)
South Holston
1986
1987
1988
1989
1991
1990
1993
1994
1995
1996
1997
1998
1999
2000
71
Appendix A. (Continued)
Year
Number Stocked
Size
Density
Source
1,000,000
5,000,000
63,780
2,000,000
351,636
1,000,000
134,633
41,313
100,691
7,751
94,725
123,848
162,991
1,000,000
71,733
fry
fry
fingerling
fry
fingerling
fry
fingerling
fingerling
fingerling
fingerling
fingerling
fingerling
fingerling
fry
fingerling
154
769
10
308
54
154
21
6
16
1
15
19
25
154
11
KS
WI
N
WI
CH
N
N
N
N
N
N
N
CH
N
KY
70
1,000,000
35,460
20,846
105,106
66,512
226,139
217,441
38,155
97,828
adult
fry
fingerling
fingerling
fingerling
fingerling
fingerling
fingerling
fingerling
fingerling
<1
389
14
8
41
26
88
85
15
38
GL
GL
N
N
KY
N
N
N
N
N
Citation
Tellico
1982
1985
1985
1987
1987
1989
1989
1990
1992
1993
1994
1995
1998
1999
2000
T. Churchill, TWRA, unpublished data
T. Churchill, TWRA, unpublished data
T. Churchill, TWRA, unpublished data
T. Churchill, TWRA, unpublished data
T. Churchill, TWRA, unpublished data
T. Churchill, TWRA, unpublished data
Peterson and Lane (1989b)
Peterson (1990)
Peterson and Negus (1992a)
Peterson and Negus (1993c)
Peterson and Negus (1994b)
Peterson and Negus (1995b)
Peterson and Negus (1998b)
Peterson and Negus (1999b)
Peterson and Negus (2000b)
Watauga
1954
1954
1985
1986
1989
1992
1994
1996
1997
1999
72
Fetterolf (1956)
Fetterolf (1956)
T. Churchill, TWRA, unpublished data
T. Churchill, TWRA, unpublished data
Peterson and Lane (1989c)
Peterson and Negus (1992b)
Peterson and Negus (1994c)
Peterson and Thurman (1996)
Peterson and Thurman (1998b)
Peterson and Thurman (1999b)
Appendix A References
Fetterolf, C. M. Jr. 1956. Stocking as a management tool in Tennessee reservoirs.
Proceedings of the Southeastern Association of Game and Fish Commissioners 10:
275-284.
Libbey, J.E. 1969. Certain aspects of the life history of the walleye, Stizostedion vitreum
vitreum (Mitchell), in Dale Hollow Reservoir, Tennessee, Kentucky, with emphasis
on spawning. Master’s thesis. Tennessee Technological University, Cookeville.
Muench, K.A. 1966. Certain aspects of the life history of the walleye, Stizostedion
vitreum vitreum, in Center Hill Reservoir, Tennessee. Master’s Thesis. Tennessee
Technological University, Cookeville.
Myhr, A. I., M. Jolley, and P. T. Copeland. 1998. Dale Hollow Reservoir annual report.
Tennessee Wildlife Resources Agency, Fisheries Report 99-35, Nashville.
Myhr, A. I., M. Jolley, and P. T. Copeland. 1999. Dale Hollow Reservoir annual report.
Tennessee Wildlife Resources Agency, Fisheries Report 00-43, Nashville.
Peterson, D. C. 1990. Tellico Reservoir annual report. Tennessee Wildlife Resources
Agency, Fisheries Report, Project Number 91-26, Nashville.
Peterson, D. C., and D. E. Lane. 1989a. South Holston Reservoir annual report.
Tennessee Wildlife Resources Agency, Fisheries Report, Project Number 4311 and
4313, Nashville.
Peterson, D. C., and D. E. Lane. 1989b. Tellico Reservoir annual report. Tennessee
Wildlife Resources Agency, Fisheries Report, Project Number 4311, Nashville.
Peterson, D. C., and D. E. Lane. 1989c. Watauga Reservoir annual report. Tennessee
Wildlife Resources Agency, Fisheries Report, Project Number 4311 and 4312,
Nashville.
Peterson, D. C., and J. A. Negus. 1992a. Tellico Reservoir annual report. Tennessee
Wildlife Resources Agency, Fisheries Report 93-27, Nashville.
Peterson, D. C., and J. A. Negus. 1992b. Watauga Reservoir annual report. Tennessee
Wildlife Resources Agency, Fisheries Report 93-28, Nashville.
Peterson, D. C., and J. A. Negus. 1993a. Norris Reservoir annual report. Tennessee
Wildlife Resources Agency, Fisheries Report 95-16, Nashville.
Peterson, D. C., and J. A. Negus. 1993b. South Holston Reservoir annual report.
Tennessee Wildlife Resources Agency, Fisheries Report 95-23, Nashville.
Peterson, D. C., and J. A. Negus. 1993c. Tellico Reservoir annual report. Tennessee
Wildlife Resources Agency, Fisheries Report 95-16, Nashville.
Peterson, D. C., and J. A. Negus. 1994a. Norris Reservoir annual report. Tennessee
Wildlife Resources Agency, Fisheries Report 95-36, Nashville.
Peterson, D. C., and J. A. Negus. 1994b. Tellico Reservoir annual report. Tennessee
Wildlife Resources Agency, Fisheries Report 95-38, Nashville.
Peterson, D. C., and J. A. Negus. 1994c. Watauga Reservoir annual report. Tennessee
Wildlife Resources Agency, Fisheries Report 95-40, Nashville.
Peterson, D. C., and J. A. Negus. 1995a. Norris Reservoir annual report. Tennessee
Wildlife Resources Agency, Fisheries Report 97-15, Nashville.
Peterson, D. C., and J. A. Negus. 1995b. Tellico Reservoir annual report. Tennessee
Wildlife Resources Agency, Fisheries Report 97-16, Nashville.
73
Appendix A References - continued
Peterson, D. C., and J. A. Negus. 1996. Norris Reservoir annual report. Tennessee
Wildlife Resources Agency, Fisheries Report 97-52, Nashville.
Peterson, D. C., and J. A. Negus. 1997. Norris Reservoir annual report. Tennessee
Wildlife Resources Agency, Fisheries Report 98-9, Nashville.
Peterson, D. C., and J. A. Negus. 1998a. Norris Reservoir annual report. Tennessee
Wildlife Resources Agency, Fisheries Report 99-9, Nashville.
Peterson, D. C., and J. A. Negus. 1998b. Tellico Reservoir annual report. Tennessee
Wildlife Resources Agency, Fisheries Report 99-11, Nashville.
Peterson, D. C., and J. A. Negus. 1999a. Norris Reservoir annual report. Tennessee
Wildlife Resources Agency, Fisheries Report 00-21, Nashville.
Peterson, D. C., and J. A. Negus. 1999b. Tellico Reservoir annual report. Tennessee
Wildlife Resources Agency, Fisheries Report 00-22 , Nashville.
Peterson, D. C., and J. A. Negus. 2000a. Norris Reservoir annual report. Tennessee
Wildlife Resources Agency, Fisheries Report 01-22, Nashville.
Peterson, D. C., and J. A. Negus. 2000b. Tellico Reservoir annual report. Tennessee
Wildlife Resources Agency, Fisheries Report 01-30, Nashville.
Peterson, D. C., and W. M. Thurman. 1995. South Holston Reservoir annual report.
Tennessee Wildlife Resources Agency, Fisheries Report 97-25, Nashville.
Peterson, D. C., and W. M. Thurman. 1996. Watauga Reservoir annual report. Tennessee
Wildlife Resources Agency, Fisheries Report 97-57, Nashville.
Peterson, D. C., and W. M. Thurman. 1997. Watauga Reservoir annual report. Tennessee
Wildlife Resources Agency, Fisheries Report 98-9, Nashville.
Peterson, D. C., and W. M. Thurman. 1998a. South Holston Reservoir annual report.
Tennessee Wildlife Resources Agency, Fisheries Report 99-26, Nashville.
Peterson, D. C., and W. M. Thurman. 1998b. Watauga Reservoir annual report.
Tennessee Wildlife Resources Agency, Fisheries Report 99-21, Nashville.
Peterson, D. C., and W. M. Thurman. 1999a. South Holston Reservoir annual report.
Tennessee Wildlife Resources Agency, Fisheries Report 00-30, Nashville.
Peterson, D. C., and W. M. Thurman. 1999b. Watauga Reservoir annual report.
Tennessee Wildlife Resources Agency, Fisheries Report 00-28, Nashville.
Peterson, D. C., and W. M. Thurman. 2000. Watauga Reservoir annual report. Tennessee
Wildlife Resources Agency, Fisheries Report 01-25, Nashville.
74
Appendix B. Number of alewives and threadfin shad captured in vertical gill nets in six Tennessee
reservoirs, July-August 1999. A 13-mm mesh net and a 19-mm mesh net were fished overnight at
each station.
Reservoir
Transect
Station
Alewife
Threadfin shad
Center Hill
Center Hill
Center Hill
Center Hill
Center Hill
Center Hill
Center Hill
Center Hill
Center Hill
Dale Hollow
Dale Hollow
Dale Hollow
Dale Hollow
Dale Hollow
Dale Hollow
Dale Hollow
Dale Hollow
Dale Hollow
Dale Hollow
Norris
Norris
Norris
Norris
Norris
Norris
Norris
Norris
Norris
Norris
South Holston
South Holston
South Holston
South Holston
South Holston
South Holston
South Holston
1
1
1
2
2
2
3
3
3
1
1
1
2
2
2
3
3
3
3
1
1
1
1
2
2
2
3
3
3
1
1
1
1
2
2
2
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
4
1
2
3
4
1
2
3
1
2
3
1
2
3
4
1
2
3
7
17
10
6
8
3
0
10
2
350
414
70
500
385
259
9
206
305
452
1
54
65
41
3
18
1
28
33
34
20
23
20
39
12
2
14
48
43
35
98
91
38
391
191
160
214
163
84
142
98
72
2
18
20
31
2
39
74
104
56
96
64
48
70
62
1
77
45
2
144
57
182
75
Appendix B (continued).
Reservoir
Transect
Station
Alewife
Threadfin shad
South Holston
South Holston
South Holston
Tellico
Tellico
Tellico
Tellico
Tellico
Tellico
Tellico
Tellico
Tellico
Tellico
Watauga
Watauga
Watauga
Watauga
Watauga
Watauga
Watauga
Watauga
Watauga
Watauga
3
3
3
1
1
1
2
2
2
3
3
3
3
1
1
1
1
2
2
2
3
3
3
1
2
3
1
2
3
1
2
3
1
2
3
4
1
2
3
4
1
2
3
1
2
3
45
88
17
13
11
6
7
7
6
7
10
3
12
493
506
0
73
179
286
1
475
403
2
320
200
410
27
64
76
103
90
88
12
8
11
0
0
0
0
0
0
0
0
7
7
14
76
Appendix C. Predicted total lengths-at-age derived from the von Bertalanffy growth model for walleyes collected from six Tennessee
reservoirs between 1998 and 2000. Total lengths given in mm.
Reservoir
Age (years)
1
2
3
4
5
6
7
8
9
Center Hill
286
430
495
525
538
544
547
548
549
Dale Hollow
301
415
485
529
556
573
583
590
Norris
286
414
479
511
527
535
539
South Holston
278
440
510
541
554
560
562
Tellico
327
413
473
516
546
567
Watauga
300
395
461
509
540
562
77
10
11
12
13
594
596
598
599
599
541
542
543
581
592
599
578
589
597
606
609
610
602