Site by Bennett Web & Design Co.
2013 SOUTHEASTERN NATURALIST 12(1):217–232
Population Attributes of Lake Trout in Tennessee Reservoirs
Drew Russell1,2,* and Phillip W. Bettoli3
Abstract - We sampled stocked Salvelinus namaycush (Lake Trout) in Watauga Lake
and South Holston Lake, TN using experimental gill nets in 2009–2010 to describe
their growth, longevity, and condition. Annuli in sagittal otoliths formed once a year
in early spring in both reservoirs. South Holston Lake (n = 99 Lake Trout) has been
stocked since 2006, and the oldest fish was age 4. Watauga Lake has been stocked
since the mid-1980s, and we collected 158 Lake Trout up to age 20. Annual mortality
for age-3 and older fish in Watauga Lake was 24%. When compared to Lake Trout in
northern lakes, Tennessee Lake Trout exhibited average to above-average growth and
longevity. Condition of Lake Trout in both reservoirs varied seasonally and tended to
be lowest in fall, but rebounded in winter and spring. Lake Trout in both reservoirs
appeared to be spatially segregated from pelagic prey fishes during summer stratification,
but growth rates and body condition were high enough to suggest that neither
system was being overstocked.
Salvelinus namaycush Walbaum (Lake Trout) are widely distributed throughout
Canada and the northern United States (Crossman 1995), predominating in
deep, cold lakes (Johnson 1976). Lake Trout are well adapted to cold oligotrophic
lakes with extensive hypolimnia and prefer temperatures of approximately 10 ±
2 °C (Magnuson et al. 1990). While they can be found in shallow water only 3
to 5 m deep in spring and fall, Lake Trout will seek cold temperatures at depths
of 60 m or more in the summer and are one of the most stenothermal freshwater
species in North America (Magnuson et al. 1990). Their large body size, high longevity,
iteroparity, great fecundity, and large eggs are attributes that contribute to
their persistence in harsh environments where recruitment can be highly variable
(Evans and Olver 1995). Lake Trout have been introduced extensively outside
of their native range (Crossman 1995). In many reservoirs in the western United
States, introduced Lake Trout populations are managed as trophy fish because of
their potential to reach large sizes (Johnson and Martinez 2000). Lake Trout can
live up to 50 years, and the current all-tackle angling world record fish (according
to the International Game Fish Association) weighed 32.65 kg. A large body
size assures low predation on adults and often places this piscivore at the top trophic
position in food webs (Vander Zanden and Rasmussen 1996). Because they
are an apex predator, introduced Lake Trout pose a serious threat to indigenous
fish species in western US lakes, including other salmonids such as Salvelinus
1Tennessee Cooperative Fishery Research Unit, Tennessee Technological University,
Cookeville, TN 38505. 2Current address - US Army Corps of Engineers, 600 Dr. Martin
Luther King Place, Louisville, KY 40202. 3US Geological Survey, Tennessee Cooperative
Fishery Research Unit, Tennessee Technological University, Cookeville, TN 38505.
*Corresponding author - email@example.com.
218 Southeastern Naturalist Vol. 12, No. 1
confluentus Suckley (Bull Trout) and Oncorhynchus clarkii Richardson (Cutthroat
Trout) (Ruzycki et al. 2003).
Lake Trout were first stocked into Tennessee waters (Dale Hollow Lake in
the Cumberland River watershed) in 1977 (Hubbs 1988). The Tennessee Wildlife
Resource Agency (TWRA) began stocking Lake Trout into Watauga Lake
in northeast Tennessee during the mid-1980s. At latitude 36°19'N, the Watauga
Lake population of Lake Trout represents one of the southernmost populations
of this species in North America. Lake Trout have also been stocked annually
into South Holston Lake since 2006. By 2009, over one million hatchery-reared
Lake Trout had been stocked into both reservoirs. During the first years of
stocking, the numbers of Lake Trout stocked were low and variable; however,
an average of more than 80,000 Lake Trout have been stocked annually into
Watauga Lake since 1999, and 50,000 have been stocked annually in South
Holston Lake since 2006. When Lake Trout are stocked each winter as age-1
individuals, they average about 152 mm (6 inches) in total length (TL) and
subsequently grow to harvestable sizes in sufficient numbers to support recreational
fisheries in both reservoirs. In a 2005 Watauga Lake creel survey, about
9% of intended fishing effort (12,903 angler-hours) was directed at “any trout”
or “Lake Trout” (Black 2006). Despite the long-running Lake Trout stocking
program, there is no published information on the ecology of Lake Trout
in either of these two Tennessee reservoirs. Both Lake Trout populations are
thought to be supported entirely by hatchery fish because (1) there has been no
indication of natural recruitment (J. Hammonds, Tennessee Wildlife Resources
Agency, Morristown, TN, pers. comm.), and (2) Lake Trout eggs require sediment-
free rocky substrate with abundant interstitial spaces to incubate (Dorr et
al. 1981, Martin and Olver 1980). These types of substrates are scarce in Watauga
and South Holston Lakes.
Lake Trout do not pose any known threats to the ecological integrity of
reservoir systems in Tennessee because of differences in habitat preferences
of Lake Trout and native species. Most indigenous fish species in Tennessee
reservoirs prefer littoral or benthic habitat, whereas Lake Trout occupy the
pelagic zone throughout most of the year. In the absence of native salmonids
or pelagic piscivores to compete with, Lake Trout introduced into Tennessee
reservoirs are filling an essentially unoccupied habitat in these ecosystems. In
addition, the apparent inability of Lake Trout to reproduce in these reservoirs
gives managers the ability to control population levels and curtail any unwanted
impact of the species by adjusting stocking rates, harvest regulations,
Our primary objective was to describe attributes of the Lake Trout populations
in Watauga Lake and South Holston Lake. Specifically, we present information
on annulus formation, longevity, growth, robustness, and mortality and contrast
some of these population attributes among seasons and between reservoirs. We
also compared growth and longevity of Tennessee Lake Trout with those of Lake
Trout populations elsewhere in North America. Growth, in particular, is one
of the most important and reliable indicators of fish health and habitat quality
2013 D. Russell1 and P.W. Bettoli 219
(DeVries and Frie 1996), and modeling growth rates is an important component
of any effective management plan.
Watauga Lake (36°31'23.85"N, 82°5'17.38"W) is a 2602-ha impoundment on
the Watauga River in the headwaters of the Tennessee River system in northeast
Tennessee. It holds the distinction of being the highest reservoir in the Tennessee
River system with a full-pool elevation of more than 597 m above mean sea level
(amsl). The Tennessee Valley Authority (TVA) constructed the dam and reservoir
in 1948, principally for flood control and hydropower generation. At full pool,
Watauga Lake has a capacity of 1.885 x 108 m3 and a shoreline length of 169 km
and is 26.2 km long (Hammonds and Peterson 2007a). It has a shoreline development
index of 9, an average depth of 7 m, and a maximum depth of 95 m. Watauga
Lake is monomictic and exhibits a heterograde dissolved oxygen (DO) profile
each summer; DO concentrations are depressed in the metalimnion, but recover
in the hypolimnion (Fig. 1). The TWRA classified Watauga Lake as mesotrophic
with a trophic index of 44.3 (Carlson 1977). As a two-story reservoir, it supports
a warmwater fishery for Micropterus salmoides Lacépède (Largemouth Bass) and
M. punctulatus Rafinesque (Spotted Bass), a coolwater fishery for M. dolomieu
Lacepède (Smallmouth Bass) and Sander vitreus Mitchill (Walleye), and a coldwater
fishery for Onchorhynchus mykiss Walbaum (Rainbow Trout), Salmo trutta
L. (Brown Trout) and Lake Trout. Pelagic forage for Lake Trout is provided by
Alosa pseudoharengus Wilson (Alewife; Vandergoot and Bettoli 2001), which
were stocked in the late 1970s.
South Holston Lake (36°19'21.52"N, 82°7'19.52"W) is a 3068-ha impoundment
on the South Fork of the Holston River (just north of Watauga Lake) that
straddles the Virginia border. The reservoir was constructed in 1950 for flood
control and power production. At full pool, South Holston Lake is 527 m amsl,
has a capacity of 3.118 x 108 m3 and a shoreline length of 293 km, and is 38.6 km
long. It has a shoreline development index of 15, an average depth of 10 m, and a
maximum depth of 75 m (Hammonds and Peterson 2007b). South Holston Lake
also has a negative heterograde DO profile when the reservoir is stratified each
summer (Fig. 1). The TWRA classified South Holston Lake as mesotrophic with
a trophic index of 44.7 (Carlson 1977). South Holston also is a two-story reservoir
that supports a warmwater fishery for Largemouth Bass and Spotted Bass, a
coolwater fishery for Smallmouth Bass and Walleye, and a coldwater fishery for
Rainbow Trout, Brown Trout, and Lake Trout. The pelagic forage base includes
both Alewives and Dorosoma petenense Günther (Threadfin Shad; Vandergoot
and Bettoli 2001).
Gill netting is a widely used method for sampling Lake Trout in northern US
and Canadian lakes (Carl 2007, Hansen et al. 2008, Madenjian et al. 2008). We
220 Southeastern Naturalist Vol. 12, No. 1
Figure 1. Dissolved oxygen (mg/L) and temperature (°C) profiles in August 2009 for
Watauga Lake and South Holston Lake.
2013 D. Russell1 and P.W. Bettoli 221
deployed sinking experimental monofilament horizontal gill nets, the most common
type of gill nets used to sample Lake Trout (e.g., Gunn et al. 1987, Trippel
1993). Experimental gill nets reduce size-selectivity biases encountered when
using nets of a single mesh size, and a broader range of size classes in the population
is vulnerable to such gear (Helser et al. 1991). Each net measured 107 m
x 3 m and consisted of 7 separate panels, each 18 m long with the following barmeasure
mesh sizes (mm): 25, 38, 51, 64, 76, 89, and 102. The use of large mesh
sizes (e.g., 102 mm) increased the probability of capturing the largest individuals
in the population (Hansen et al. 1997). Nets were hung on a 2:1 basis, whereby
4 meshes are hung in the space of 2 stretched meshes. Sampling locations were
chosen based on information obtained from Lake Trout anglers, fishing reports,
and location of fish using sonar. Lake Trout thermal preferences and minimum
oxygen requirements are well documented (Christie and Regier 1988, Magnuson
et al. 1990, Stewart et al. 1983); therefore, we measured temperature and
dissolved oxygen profiles to target Lake Trout. Both lakes were sampled on six
different occasions from late May 2009 to February 2010. Thirty gill nets were
set in South Holston Lake and 31 in Watauga Lake over four seasons; we attempted
to set at least five gill nets per sampling trip. Each reservoir was sampled twice
in May 2009 (Spring), once in July and once in August 2009 (Summer), once in
September 2009 (Fall), and once in either January or February 2010 (Winter).
Netting sites were not fixed, though nets were most often deployed in the deep
water of the lower reaches of both reservoirs. Nets were set perpendicular to the
shoreline or on offshore humps with the lead line on the bottom. Nets were set
at dusk and retrieved the following morning. An electric line hauler (Ace Line
Hauler™ Model Number 99481, Nanaimo, BC, Canada) was used to retrieve
nets. Weight (g), total length (mm), and sex of each Lake Trout were recorded,
as well as the mesh size that captured each fish. We also enumerated all other
species caught (i.e., bycatch). In order to better estimate longevity, growth, and
maximum size, we also posted notices at marinas on each reservoir requesting
that anglers retain Lake Trout heads (and their total lengths) in the hope that we
could collect otoliths from some large individuals.
Estimating population parameters
Scales have traditionally been used for aging Lake Trout because their collection
is nonlethal. Although scales are adequate for aging immature Lake Trout,
the accuracy and precision of scale ages declines considerably after sexual maturity
(Casselman 1987, Sharp and Bernard 1988). We examined sagittal otoliths
because they are considered the most accurate bony structure for estimating age
of slow-growing, long-lived species such as Lake Trout (Beamish and McFarlane
1983) and are better indicators than scales of true age of Lake Trout (Casselman
1983, Power 1978, Sharp and Bernard 1988). Otoliths were removed from each
Lake Trout captured in gill nets or by recreational anglers. Otoliths were cleaned
in bleach (sodium hypochlorite) to remove any adhering tissue, rinsed in deionized
water, and stored dry in paper envelopes. Otoliths were then embedded in
epoxy and sectioned along the transverse axis of the nucleus with an Isomet™
222 Southeastern Naturalist Vol. 12, No. 1
low-speed saw and examined under 100x magnification using transmitted light
with a compound microscope. The number of annuli on each cross section was
counted independently twice by the same reader; if the counts did not agree, the
otolith was read a third time before an age was assigned. Mean marginal increments
also were measured on each otolith and plotted against season of capture
to estimate the time of annulus formation and to confirm that opaque bands were
annuli. The marginal increment was measured as the distance from the distal
margin of the outermost annulus to the otolith edge (Casselman 1987). The greatest
marginal increments would occur just before an annulus was laid down; the
smallest would occur just after annulus formation.
Total annual mortality (A, %) was estimated for Lake Trout in Watauga Lake,
which had the oldest population of the two reservoirs sampled. The natural
logarithms of catch-at-age were modeled against age and a weighted catch-curve
regression was used to estimate the slope, z, of the descending limb of the catch
curve (i.e., instantaneous mortality). Total annual mortality was estimated with
the formula A = 1 - e-Z (Miranda and Bettoli 2007). Only fish captured in gill nets
were used to estimate mortality (i.e., angler-caught fish were excluded from this
analysis), and only those age-classes fully recruited to the gear were incorporated
into the catch-curve (i.e., age classes in the left, ascending limb of the catch curve
Growth rates of Lake Trout were described using the von Bertalanffy growth
Lt = L∞ (1 - e-K[t - t
where Lt is the total length in time t (years), L∞ is the maximum theoretical attainable
length (mm), K is the growth coefficient, and t0 is the time in years when
the length theoretically would be zero (von Bertalanffy 1957). The parameters of
the model were estimated using Fisheries Analysis and Simulation Tools (FAST)
software (Slipke and Maceina 2000). Growth rates of Lake Trout in Watauga
Lake and South Holston Lake were then compared to their growth in several
northern US lakes for which we could obtain estimates of those same growth
model parameters and where otoliths were used to age fish. Data on Lake Trout
populations from the following eastern US lakes were used in the comparison:
Moosehead Lake, ME and Sebago Lake, ME (P. Johnson, State of Maine Department
of Inland Fisheries and Wildlife, Greenville, ME, unpubl. data); Piseco
Lake, NY (S. Jameson, New York State Department of Environmental Conservation,
Ray Brook, NY, unpubl. data). Lake Superior Lake Trout also were included
in the comparisons (T. Halpern, Minnesota Department of Natural Resources,
Grand Rapids, MN, unpubl. data), although they are known to behave differently
than most inland lake populations because of morphotypes that can differ in their
biology (e.g., Bronte 1993, Burnham-Curtis and Bronte 1996, Khan and Qadri
1970). The parameter ω, which is the product of the theoretical maximum length
L∞, and the growth coefficient K (Gallucci and Quinn 1979), was calculated for
each population; this parameter has been shown to be a useful metric for comparing
growth among populations (Gangl and Pereira 2003, OMNR 1983).
2013 D. Russell1 and P.W. Bettoli 223
The robustness of Lake Trout in our study reservoirs was qualitatively
compared to the condition exhibited by other North American populations
by calculating relative weights. The standard weight equation was provided by
Piccolo et al. (1993). We used analysis-of-covariance (ANCOVA) to evaluate
differences in adjusted mean weights of Lake Trout among seasons and between
the two Tennessee reservoirs. In these analyses, log10(weight) was the response
variable, log10(total length) was the covariable, and season (or reservoir) was
the independent variable. Adjusted mean weights were not compared unless the
slopes of the log10(weight):log10(total length) regression lines were similar (P >
0.05); the interaction term testing the slopes was subsequently dropped when
adjusted means were tested. Statistical Analysis System software (SAS Institute,
Inc. 1989) was used to perform analyses of covariance, with an alpha level of
0.05 in tests of statistical significance.
Using gill nets, we collected 99 Lake Trout from South Holston Lake
(260–636 mm TL) and 158 Lake Trout from Watauga Lake (251–842 mm
TL). In addition to the gill net catches, anglers provided us with the skulls
and lengths of five Lake Trout from South Holston Lake (393–464 mm TL)
and 12 Lake Trout from Watauga Lake (431–635 mm TL). As many as 12
Lake Trout in a single net were caught during spring and summer in South
Holston Lake, and the greatest catch in a single net in Watauga Lake (17 Lake
Trout) occurred in the fall. The depths at which nets were set depended on
temperature and dissolved oxygen profiles and thus differed each season. For
instance, the shallowest nets were set in spring in each reservoir, when the
average depth of each net ranged from 4.2 to 31.3 m in South Holston Lake
and 9.5 to 28.9 m in Watauga Lake. Average net depths were the deepest in the
fall, ranging from 27.6 to 46.0 m in South Holston Lake and 20.7 to 43.9 m in
Watauga Lake. The most common piscivores (i.e., potential competitors with
Lake Trout) collected in gill nets (both reservoirs combined; all seasons) were
Walleye (n = 310), Ictalurus punctatus Rafinesque (Channel Catfish; n = 58),
Rainbow Trout (n = 49), and Smallmouth Bass (n = 25).
We collected otoliths from 20 Lake Trout reared at the Dale Hollow National
Fish Hatchery (the source of all Lake Trout stocked in Tennessee) in December
2009, approximately one month before they were stocked, to check for prestocking
annuli. No opaque bands were observed on any of those otoliths. The
two ages assigned independently to otoliths removed from Lake Trout collected
in South Holston Lake and Watauga Lake agreed within 1 year or less for 88%
of the otoliths examined. Otoliths exhibited alternating translucent and opaque
zones, and marginal increments increased steadily from a low in spring 2009 to a
high in winter 2010, which indicated that a single opaque band was formed once
per year between late winter and spring. Three Lake Trout that were stocked in
January 2010 were caught in May 2010, and the number of annuli on those three
known-age fish were in agreement (i.e., one annulus was present on each of the
224 Southeastern Naturalist Vol. 12, No. 1
otoliths). Three year classes of Lake Trout from Watauga Lake that were missing
from our samples (1991, 1993, and 1994) corresponded with years when no Lake
Trout were stocked. These aforementioned observations support the conclusion
that annuli were laid down once a year in the otoliths we examined.
Lake Trout in Watauga Lake ranged from age 1 to age 20, whereas the South
Holston population ranged from age 1 to age 4. Lake Trout from the 2006 year
class represented the highest percentage of Lake Trout collected in both Watauga
Figure 2. Age distributions of Lake Trout collected in gill nets at Watauga Lake and South
Holston Lake, May 2009–February 2010.
2013 D. Russell1 and P.W. Bettoli 225
Table 1. Mean total length (TL, mm) and frequencies for each age class of lake Trout caught in gill
nets or supplied by anglers at Watauga Lake and South Holston Lake, May 2009–February 2010.
One outlier from Watauga Lake was excluded from the analysis.
Watauga Lake South Holston Lake
Age n Mean TL n Mean TL
1 2 259 2 299
2 13 403 17 381
3 38 460 54 493
4 30 517 31 514
5 24 544
6 24 574
7 11 581
8 6 670
9 4 683
10 3 745
11 2 763
12 3 809
13 3 807
14 3 800
15 1 759
17 1 758
20 1 735
Total 169 104
Lake (22%) and South Holston Lake (45%) (Fig. 2). The instantaneous mortality
rate (z) for age 3 and older Lake Trout in Watauga Lake was 0.268, which corresponds
to a total annual mortality rate (A) of 24%. The longest and heaviest fish
collected from Watauga Lake was an 842-mm-TL, 7.21-kg, age-13 female. The
longest fish from South Holston Lake was a 636-mm-TL, 2.23-kg, age-4 female,
and the heaviest was a 604-mm-TL, 2.46-kg age-3 female.
The von Bertalanffy model fit to mean length-at-age data for all Lake Trout
(gill-netted and angler-caught; Table 1) yielded theoretical asymptotic maximum
total lengths (i.e., L∞) of 809 mm and 647 mm in Watauga Lake and South
Holston Lake, respectively. However, to produce potentially more accurate
growth curves, we fixed L∞ as the total length of the current state record Lake
Trout (from Watauga Lake [940 mm]) and we solved for the other parameters of
the von Bertalanffy growth model for both populations. Growth of Lake Trout in
each reservoir was then best described by:
Watauga Lake: Lt = 940(1 - e-0.109[t + 2.823])
South Holston Lake: Lt = 940(1 - e-0.149[t + 1.588]).
Values of the growth parameter ω for Lake Trout in Watauga Lake and
South Holston Lake fell within the bounds of the growth rates for Lake Trout
in northern lakes, with values of 102.5 and 140.1, respectively (Table 2). Lake
Trout lived longer in Watauga Lake than in five of the six northern lakes we
used in our comparisons; in Lake Superior, slow-growing Lake Trout lived up
to age 37.
226 Southeastern Naturalist Vol. 12, No. 1
The weight-length relationships for Lake Trout in each reservoir were best
described by the following equations:
Watauga Lake: log10WT = 3.190 log10TL - 5.502 (n = 157, r2 = 0.98)
South Holston Lake: log10WT = 3.329 log10TL - 5.893 (n = 98, r2 = 0.98).
There was no significant difference among seasons in slopes of the
log10(TL):log10(WT) regression lines in Watauga Lake (P = 0.274) or South
Holston Lake (P = 0.0560); thus, adjusted mean weights could be computed and
compared. Season was a significant source of variation in the robustness of Lake
Trout in Watauga Lake (ANCOVA: F = 11.57; df = 3, 152; P < 0.0001) and South
Holston Lake (F = 1285.84; df = 3, 93; P < 0.0001). Lake Trout in Watauga Lake
were most robust in the spring, while there were no significant differences among
adjusted mean weights in other seasons. Lake Trout in South Holston Lake were
most robust in spring and winter and least robust in fall (Table 3).
The slopes of the log10(TL):log10(WT) regression lines were similar between the
two lakes when data were pooled over all seasons and both sexes (F = 3.53; df = 1,
251; P = 0.0614), and Lake Trout robustness in each reservoir was similar (F = 0.13;
df = 1, 252; P = 0.7186). In terms of relative weights, the condition of Lake Trout in
each reservoir was virtually identical; mean relative weights were 102.8 (SE = 1.1)
in Watauga Lake and 102.5 (SE = 0.98) in South Holston Lake (Fig. 3). The relative
weight plots also demonstrate that Tennessee Lake Trout were in good condition
relative to Lake Trout populations elsewhere in North America.
Table 3. Adjusted mean weights for Lake Trout in Watauga Lake and South Holston Lake, 2009–
2010. Pooled mean total lengths at Watauga Lake and South Holston Lake were 548 mm and 482
mm, respectively. Seasonal values within each lake that share a letter were statistically similar
(P > 0.05). Slopes of the seasonal log10 (total length):log10 (weight) regression lines at each lake
were similar (P > 0.05).
Season Watauga South Holston
Spring 1652B 1069BC
Summer 1464A 1027B
Fall 1422A 941A
Winter 1387A 1099C
Table 2. Parameters of the von Bertalanffy growth model, the growth parameter ω, and maximum
age of stocked Lake Trout from Watauga Lake and South Holston Lake, 2009–2010, and for wild
and stocked Lake Trout from lakes within the natural range of Lake Trout in the United States.
Lake, State (source) K L∞ ω Maximum age
Sebago, ME (wild) 0.290 589 170.8 9
Moosehead , ME (stocked) 0.361 473 170.8 11
Piseco, NY (wild) 0.269 630 169.5 7
S. Holston, TN (stocked) 0.149 940 140.1 4
Moosehead , ME (wild) 0.186 627 116.6 14
Sebago , ME (stocked) 0.121 940 113.7 9
Watauga, TN (stocked) 0.109 940 102.5 20
Lake Superior, MN (both) 0.069 1029 71.0 37
2013 D. Russell1 and P.W. Bettoli 227
King et al. (1999) reported that Lake Trout grew slower in years of early
stratification; however, growth was not otherwise associated with stratification
variables, (e.g., warmer epilimnion, larger thermal gradient, shallower thermocline),
which suggested that springtime feeding on littoral prey was a major
determinant of growth for Lake Trout. Fry and Kennedy (1937) and Martin
Figure 3. Relative weights versus total length for Lake Trout in Watauga Lake and South
Holston Lake, May 2009–February 2010.
228 Southeastern Naturalist Vol. 12, No. 1
(1970) also suggested that seasonal migration to the hypolimnion usually marks
cessation of feeding by most Lake Trout (except the largest individuals, which
become cannibalistic in Lake Opeongo, ON, Canada). This scenario appears to
be the case in Watauga Lake and South Holston Lake as evidenced by increases
in robustness of Lake Trout in both reservoirs after destratification occurred in
In six small Canadian lakes with favorable abiotic conditions (i.e., cold temperatures,
high dissolved oxygen concentrations), competition with other fish
species in the hypolimnion, more than water quality, stocking season, or stocking
size, appeared to affect survival and growth of stocked Lake Trout (Gunn et al.
1987). Powell et al. (1986) found that body condition of stocked Lake Trout in
eight lakes in northeastern Ontario, Canada, declined with increasing abundance
of coregonids, suggesting that competition for food was affecting growth. In
contrast, there is likely little competition between Lake Trout and other fish species
in the hypolimnions of Watauga Lake and South Holston Lake, especially
in the fall as evidenced by low bycatch rates. We caught (combined) only 6–11
Walleye, Rainbow Trout, and Channel Catfish in 5–6 nets set in each reservoir
in the fall, compared to catches in winter of 29–39 of those same three species
in 5–6 nets and catches in summer of 98–105 of those same piscivores in 10–11
nets. Intraspecific competition as well as separation from forage during stratification
are probably the two most important factors regulating Lake Trout growth in
Tennessee reservoirs during periods of intense stratification.
The maximum age of Lake Trout in Watauga Lake (20 years) is consistent
with the general observation for many species that slow-growing individuals tend
to live longer (Cushing 1968, Metcalfe and Monaghan 2003); that is to say, Lake
Trout in Watauga Lake grew slower than most of their northern US counterparts
but lived longer. Lake Trout in Watauga Lake lived about as long as Lake Trout
in 63 southern Canadian lakes (mean = 23.8 years) but not nearly as long as
Lake Trout in 62 northern Canadian Lakes (mean = 34.3 years; McDermid et al.
2010). It remains to be seen whether the recently stocked, young population of
fast-growing Lake Trout in South Holston Lake will follow the expected pattern
and live shorter lives than Lake Trout in nearby Watauga Lake.
The current TWRA regulations for Lake Trout on both study lakes limit
anglers to two Lake Trout per day with no length limit. No minimum length
limit exists because catch-and-release mortality of undersized Lake Trout would
undoubtedly be high during warmer months, perhaps as high as the catch-andrelease
mortality that Striped Bass experience (67%) when caught and released in
Tennessee reservoirs during summer (Bettoli and Osborne 1998). The likelihood
of high catch-and-release mortality limits the possibility of establishing typical
trophy-fish management practices such as a protective slot limit that encourages
recruitment to larger lengths. However, with control over stocking rates
and the implementation of the sampling protocols described herein, the TWRA
can ensure that Watauga Lake and South Holston Lake will continue to produce
trophy Lake Trout and provide a unique angling experience for anglers in the
southeastern United States.
2013 D. Russell1 and P.W. Bettoli 229
The use of trade, product, industry, or firm names or products is for informative
purposes only and does not constitute an endorsement by the US Government or the US
Geological Survey. Funding for this research was provided by the Tennessee Wildlife
Resources Agency, the Center for the Management, Utilization, and Protection of Water
Resources at Tennessee Technological University (TTU), and the USGS Tennessee Cooperative
Fishery Research Unit. We extend our thanks to J. Hammonds and S. Henagar for
their help in the field, as well as the many TTU graduate students and anglers (especially
Rob and Mary Kelly) who volunteered their time and fish carcasses, respectively. This
manuscript benefited from constructive comments on earlier drafts by H.T. Mattingly,
H.T. Andrews, S. Reeser, M.C. Quist, and two anonymous reviewers.
Beamish, R.J., and G.A. McFarlane. 1983. The forgotten requirement for age validation
in fisheries biology. Transactions of the American Fisheries Society 112:735–743.
Bettoli, P.W., and R.S. Osborne. 1998. Hooking mortality of behavior of Striped Bass
following catch-and-release angling. North American Journal of Fisheries Management
Black, P. 2006. Tennessee Reservoir creel survey 2005 results. Final Report. Tennessee
Wildlife Resources Agency, Nashville, TN.
Bronte, C.R. 1993. Evidence of spring spawning Lake Trout in Lake Superior. Journal of
Great Lakes Research 19:625–629.
Burnham-Curtis, M.K., and C.R. Bronte. 1996. Otoliths reveal a diverse age structure for
humper Lake Trout in Lake Superior. Transactions of the American Fisheries Society
Carl, L.M. 2007. Lake Trout demographics in relation to Burbot and Coregonine
populations in the Algonquin Highlands, Ontario. Environmental Biology of Fishes
Carlson, R.E. 1977. A trophic state index for lakes. Limnology and Oceanography
Casselman, J.M. 1983. Age and growth assessment of fish from their calcified structures:
Techniques and tools. Proceedings of the International Workshop on Age Determination
of Oceanic Pelagic Fishes: Tunas, Billfishes, and Sharks. NOAA (National
Oceanic and Atmospheric Administration) Technical Report NMFS (National Marine
Fisheries Service) 8:1–17.
Casselman, J.M. 1987. Determination of age and growth. Pp. 209–242, In A.H. Weatherly
and H.S. Gill (Eds.). The Biology of Fish Growth. Academic Press, London, UK.
Christie, G.C., and H.A. Regier. 1988. Measures of optimal thermal habitat and their
relationship to yields for four commercial fish species. Canadian Journal of Fisheries
and Aquatic Sciences 45:301–314.
Crossman, E.J. 1995. Introduction of the Lake Trout, Salvelinus namaycush, in areas
outside its native distribution: A review. Journal of Great Lakes Research 21(Supplement):
Cushing, D.H. 1968. Fisheries Biology: A Study in Population Dynamics. University of
Wisconsin Press, Madison, WI.
230 Southeastern Naturalist Vol. 12, No. 1
Devries, D.R., and R.V. Frie. 1996. Determination of age and growth. Pp. 483–512, In
B.R. Murphy and D.W. Willis (Eds). Fisheries Techniques. American Fisheries Society,
Bethesda, MD. 732 pp.
Dorr, J.A., III, D.V. O’Connor, N.R. Foster, and D.J. Jude. 1981. Substrate conditions
and abundance of Lake Trout eggs in a traditional spawning area in southeastern Lake
Michigan. North American Journal of Fisheries Management 1:165–172.
Evans, D.O., and C.H. Olver. 1995. Introduction of Lake Trout (Salvelinius namaycush)
to inland lakes of Ontario, Canada: Factors contributing to successful colonization.
Journal of Great Lakes Research 21(Supplement 1):30–53.
Fry, F.E.J., and W.A. Kennedy. 1937. Report on the 1936 Lake Trout investigation, Lake
Opeongo, Ontario. University of Toronto Studies, Biological Series 42. (Publication
of the Ontario Fisheries Research Laboratory 54:1–20).
Gallucci, V.F., and T.J. Quinn II. 1979. Reparameterizing, fitting, and testing a simple
growth model. Transactions of the American Fisheries Society 108:14–25.
Gangl, S.R., and D.L. Pereira. 2003. Biological performance indicators for evaluating
exploitation of Minnesota’s large-lake Walleye fisheries. North American Journal of
Fisheries Management 23:1303–1311.
Gunn, J.M., M.J. McMurtry, J.N. Bowlby, J.M. Casselman, and V.A. Liimatainen. 1987.
Survival and growth of stocked Lake Trout in relation to body size, stocking season,
lake acidity, and biomass of competitors. Transactions of the American Fisheries
Hammonds, J., and D.C. Peterson. 2007a. Watauga Reservoir Annual Report 2005. Tennessee
Wildlife Resources Agency, Region IV, Morristown, TN.
Hammonds, J., and D.C. Peterson. 2007b. South Holston Reservoir Annual Report 2005.
Tennessee Wildlife Resources Agency, Region IV, Morristown, TN.
Hansen, J.M., C.P. Madenjian, J.H. Selgeby, and T.E. Helser. 1997. Gillnet selectivity
for Lake Trout (Salvelinus namaycush) in Lake Superior. Canadian Journal of Aquatic
Hansen J.M., N.J. Horner, M. Liter, M.P. Peterson, and M.A. Maiolie. 2008. Dynamics
of an increasing Lake Trout population in Lake Pend Oreille, Idaho. North American
Journal of Fisheries Management 28:1160–1171.
Helser, T.E., R.E. Condrey, and J.P. Geaghan. 1991. A new method of estimating gillnet
selectivity, with an example for Spotted Seatrout, Cyocion nebulosus. Canadian Journal
of Aquatic Sciences 48:487–492.
Hubbs, D.W. 1988. Assessment of spawning habitat of Lake Trout (Salvelinus namaycush)
and Muskellunge (Esox masquinongy) in Dale Hollow Reservoir. M.Sc. Thesis.
Tennessee Technological University, Cookeville, TN. 29 pp.
Johnson, B.M., and P.J. Martinez. 2000. Trophic economics of Lake Trout management
in reservoirs of differing productivity. North American Journal of Fisheries Management
Johnson, L. 1976. Ecology of arctic populations of Lake Trout, Salvelinus namaycush,
Lake Whitefish, Coregonus clupeaformis, Arctic Char, S. alpinus, and associated
species in unexploited lakes of the Canadian Northwest Territories. Journal of the
Fisheries Research Board of Canada 33:2459–2488.
Khan, N.Y., and S.U. Qadri. 1970. Morphological differences in Lake Superior Lake
Char. Journal of the Fisheries Research Board of Canada 27:161–167.
2013 D. Russell1 and P.W. Bettoli 231
King, J.R., B.J. Shuter, and A.P. Zimmerman. 1999. Empirical links between thermal
habitat, fish growth, and climate change. Transactions of the American Fisheries Society
Madenjian, C.P., M.P. Ebener, and T.J. Desorcie. 2008. Lake Trout population dynamics
at Drummond Island Refuge in Lake Huron: Implications for future rehabilitation.
North American Journal of Fisheries Management 28:979–992.
Magnuson, J.J., Meisner, J.D., and Hill, D.K. 1990. Potential changes in the thermal habitat
of Great Lakes fish after global climate warming. Transactions of the American
Fisheries Society 119:254–264.
Martin, N.V. 1970. Long-term effects of diet on the biology of the Lake Trout and the
fishery in Lake Opeongo, Ontario. Journal of the Fisheries Research Board of Canada
Martin, N.V., and C.H. Olver. 1980. The lake charr Salvelinus namaycush. Pp. 205–277,
In E.K. Balon (Ed.). Charrs: Salmonid Fishes of the Genus Salvelinus. Dr. W. Junk,
The Hague, The Netherlands.
McDermid, J.L., B.J. Shuter, and N.P. Lester. 2010. Life-history differences parallel environmental
differences among North American Lake Trout (Salvelinus namaycush)
populations. Canadian Journal of Fisheries and Aquatic Sciences 67:314–325.
Metcalfe, N.B. and P. Monaghan. 2003. Growth versus lifespan: Perspectives from evolutionary
ecology. Experimental Gerontology 38:935–940.
Miranda, L.E., and P.W. Bettoli. 2007. Mortality. Pp. 229–277, In C. Guy and M. Brown
(Eds.). Analysis and Interpretation of Freshwater Fisheries Statistics. American Fisheries
Society Special Publication, Bethesda, MD.
Ontario Ministry of Natural Resources (OMNR). 1983. The identification of overexploitation.
OMNR, Report of Strategic Planning for Ontario Fisheries Working Group 15,
Toronto, ON, Canada.
Piccolo, J.J., W.A. Hubert, and R.A. Whaley. 1993. Standard weight equation for Lake
Trout. North American Journal of Fisheries Management 13:401–404.
Powell, M.J., M.F. Bernier, S.J. Kerr, G. Leering, M. Miller, W. Samis, and M. Pellegrini.
1986. Returns of hatchery-reared Lake Trout from eight lakes in northeastern Ontario.
Ontario Ministry of Natural Resources, Ontario Fisheries Technical Report Series 22,
Toronto, ON, Canada.
Power, G. 1978. Fish population structure in Arctic lakes. Journal of the Fisheries Research
Board of Canada 35:53–59.
Ruzycki, J.R., D.A. Beauchamp, and D.L. Yule. 2003. Effects of introduced Lake Trout
on native Cutthroat Trout in Yellowstone Lake. Ecological Applications 13:23–37.
SAS Institute, Inc. 1989. SAS/STAT User’s Guide, Version 6, 4th Ed. Vol. 2. SAS Institute,
Inc., Cary, NC.
Sharp, D., and D.R. Bernard. 1988. Precision of estimated ages of Lake Trout from five
calcified structures. North American Journal of Fisheries Management 8:367–372.
Shram, S.T., and M.C Fabrizio. 1998. Longevity of Lake Superior Lake Trout. North
American Journal of Fisheries Management 18:700–703.
Slipke, J.W., and M.J. Maceina. 2000. Fishery analyses and simulation tools. Auburn
University, Auburn, AL.
Stewart, D.J., W. Weininger, D.V. Rottiers, and T.A. Edsall. 1983. An energetics model
for Lake Trout: Application to the Lake Michigan population. Canadian Journal of
Fisheries and Aquatic Sciences 40:681–698.
232 Southeastern Naturalist Vol. 12, No. 1
Trippel, E.A. 1993. Relations of fecundity, maturation, and body size of Lake Trout, and
implications for management in Northwestern Ontario lakes. North American Journal
of Fisheries Management 13:64–72.
Vander Zanden, M.J., and J.B. Rasmussen. 1996. A trophic position model of pelagic
food webs: Impact on contaminant bioaccumulation in Lake Trout. Ecological Monographs
Vandergoot, C.J., and P.W. Bettoli. 2001. Evaluation of current management practices
and assessment of recruitment, growth, and condition of Walleyes in Tennessee reservoirs.
Fisheries Report 01-44, Tennessee Wildlife Resources Agency, Nashville, TN.
von Bertalanffy, L. 1957. Quantitative laws in metabolism and growth. Quarterly review
of Biology 32:217–231.