Brook Trout Strains Research Articles

Capture of Spawning Brook Trout by Electrofishing Does Not Impair Embryo Survival

AbstractElectrofishing is widely used to capture fish in freshwater systems. Fisheries assessment and fish culture activities that occur during spawning do so in the absence of a meaningful base of evidence about the potential effects of electrofishing on fish reproduction. In this laboratory experiment, we assessed whether electrofishing adult Brook Trout Salvelinus fontinalis affected the survival of their embryos. We used two genetically distinct strains of Brook Trout (domestic and wild‐origin strains) to do so. Both strains and sexes of fish were exposed to pulsed‐DC electrofishing techniques in a fully factorial design (i.e., male shocked, female shocked, both parents shocked, or neither parent shocked [control]), after which their incubating offspring were monitored for survival to the eyed egg, alevin, and fry stages. We did not detect any effects of our electrofishing treatment or interactions with the sex or strain of the fish exposed to electrofishing, suggesting that electrofishing did not negatively impact gamete viability. Our results support the use of responsible electrofishing to collect spawning salmonids for the purpose of gamete collection for hatchery rearing.

Biological Consequences of the Coaster Brook Trout Restoration Stocking Program in Lake Superior Tributaries within Pictured Rocks National Lakeshore

AbstractThe coaster Brook Trout Salvelinus fontinalis is a Lake Superior ecotype representing intraspecific variation that has been impacted by habitat loss and overfishing. Hatchery strains of Brook Trout derived from populations in Lake Superior were stocked into streams within Pictured Rocks National Lakeshore, Michigan, as part of an effort to rehabilitate adfluvial coaster Brook Trout. Wild and hatchery Brook Trout from three streams (Mosquito River, Hurricane River, and Sevenmile Creek) were examined for movement behavior, size, physiology, and reproductive success. Behavior and size of the stocked fish were similar to those of wild fish, and less than 15% of the stocked, tagged Brook Trout emigrated from the river into which they were stocked. There was little evidence of successful reproduction by stocked Brook Trout. Similar to the results of other studies, our findings suggest that the stocking of nonlocal Brook Trout strains where a local population already exists results in limited natural reproduction and should be avoided, particularly if the mechanisms governing the ecotype of interest are poorly understood.Received April 1, 2012; accepted November 26, 2012

Comparison of growth physiology, morphology, and smolt indicators in juvenile Lake Superior brook trout (Salvelinus fontinalis) strains in reference to life history variation

Lake Superior supports fluvial, adfluvial, and lacustrine populations of brook trout ( Salvelinus fontinalis ). Adfluvial and lacustrine populations (termed coasters) are known for their large size and are coveted by anglers; however, little is known about their migratory habits or physiology. This study examined physiology and morphology of age 1+ lacustrine, adfluvial, and fluvial strains of brook trout in a laboratory setting. All strains in the study grew; however, there were no differences in growth rate, condition, relative mass, morphology, white muscle metabolic enzymes, or gill Na+,K+-ATPase that clearly associated with putative life history strategy. Both thyroxine and triiodothyronine varied over the study period, and the fluvial (resident) strain consistently showed lower thyroid hormone levels than the three coaster strains. We conclude that the populations compared differed at the strain level, but do not show physiological or morphological variability that clearly associates with life history strategy; the exception was that populations demonstrating the coaster phenotype had increased concentrations of plasma thyroid hormones, which may be linked to growth potential or other coaster-related characteristics such as migration.

Variation in Acute Thermal Tolerance within and among Hatchery Strains of Brook Trout

AbstractThe ability of coldwater species and populations to respond to temperature increases associated with climate change will depend on the existing adaptive potential within and among populations. Brook trout Salvelinus fontinalis is a valued coldwater species that has been widely stocked across its native range as well as extensively introduced in western North America. We investigated the thermal tolerance of the three primary brook trout hatchery strains used in Ontario (Dickson Lake, Lake Nipigon, and Hill's Lake strains) and the thermal tolerance of a brook trout subspecies, Aurora trout S. fontinalis timagamiensis; all strains were reared in a common hatchery environment. In addition to comparing the strains’ responses to acute thermal stress, we also examined variability in temperature tolerance among families within several of these strains. Evidence for significant differences in temperature tolerance was observed both within and among the strains, with Aurora trout showing the least capacity to cope with higher temperatures. The results of this study suggest that thermal performance of brook trout populations will be under substantial selective pressure as water temperatures increase and that strains with existing tolerances for warmer conditions will be better equipped to handle these anticipated changes.

Heritability of morphology in brook trout with variable life histories.

Distinct morphological variation is often associated with variation in life histories within and among populations of both plants and animals. In this study, we examined the heritability of morphology in three hatchery strains of brook trout (Salvelinus fontinalis), which were historically or are currently used for stocking and supplementation of both migratory and resident ecotypes in the upper Great Lakes region. In a common garden experiment, significant variation in body morphology was observed within and across populations sampled at three time periods. The most notable differences among strains were differences in dorso-ventral body depth and the shape of the caudal peduncle, with some differences in the anterior-posterior placement of the dorsal and ventral fins. Variation with and among 70 half-sib families indicates that heritabilities of morphology and body size were significant at most developmental time points both within and across strains. Heritabilities for morphological characters within strains ranged from 0 to 0.95 across time points. Significant within-strain heritabilities for length ranged from 0 to 0.93 across time points and for weight ranged from 0 to 0.88. Significant additive genetic variation exists within and across hatchery brook trout strains for morphology and size, indicating that these traits are capable of responding to natural or artificial selection.

Differences in Incubation Period and Survival of Embryos among Brook Trout Strains

The incubation period and survival of brook trout Salvelinus fontinalis embryos were compared among four genetically different strains: Temiscamie (Quebec), Assinica (Quebec), Horn Lake (Adirondack), and Little Tupper Lake (Adirondack). Eggs were fertilized and then incubated under cold (mean, 5.1°C) and warm (mean, 9.4°C) thermal regimes, and the accumulated degree-days and days to 100% hatch were recorded. Within all strains, embryos incubated under the warm thermal regime accumulated more degree-days to 100% hatch than embryos incubated under the cold regime. Degree-days to hatch differed between the two thermal regimes, ranging from 457 to 672 (P < 0.001). Mean degree-days to hatch also differed among strains (P < 0.001). Under the cold regime, Assinica strain embryos developed the fastest and hatched after the fewest degree-days (457), whereas Temiscamie strain embryos developed the slowest (549 degree-days). The two Adirondack strains developed at similar rates (Horn Lake, 486 degree-days; Little Tupper Lake, 490 degree-days). Under the warm regime, Assinica and Temiscamie strains developed the slowest (672 and 654 degree-days, respectively), whereas the Adirondack strains developed the fastest and at similar rates (Little Tupper Lake, 588 degree-days; Horn Lake, 593 degree-days). The Assinica strain embryos incubated in cold and warm thermal regimes showed identical times to 100% hatch (91 d). The other three strains hatched from 8.5 to 12.5 d sooner in the warm regime than in the cold regime. Survival among the four strains was lower at 9.4°C (40–57%) than at 5.1°C (60–73%; P < 0.001). The differences in incubation period were likely caused by genetic differences among strains because the groups of embryos were incubated in physically identical environments with a common water source. The similarity in embryonic development between the two Adirondack strains may reflect an important local geographical adaptation different from that of the Quebec strains, which originated from more northerly populations.

Hatchery Performance Attributes of Nipigon, Assinica, and Iron River Strains of Age-0 Brook Trout

The fingerling hatchery performance attributes of brook trout Salvelinus fontinalis of Lake Nipigon origin were compared with those of domesticated (Assinica) and nondomesticated (Iron River) strains of this species in a 150-d laboratory experiment. Despite similar initial sizes, the final mean length and weight of the Assinica strain (134.9 mm and 26.3 g) were significantly greater than those of the Nipigon (112.6 mm and 13.6 g) and Iron River (111.2 mm and 14.6 g) strains. Specific growth rates differed significantly among strains, with Assinica fish having the greatest mean daily percent increases in length and weight (0.98% and 3.10%, respectively), followed by the Iron River (0.93% and 3.03%) and Nipigon (0.86% and 2.69%) strains. The mean daily absolute rates of growth in length and weight were similar in the Nipigon and Iron River strains but significantly lower than for the Assinica strain. Survival rates and food conversion efficiency estimates were not significantly different among the three strains of brook trout. Relative weight values were significantly greater for Assinica (96.4%) and Iron River (94.0%) fish than for Nipigon (87.0%) fish. Based on these results, we recommend that fingerling Nipigon brook trout be reared more like nondomesticated strains of this species, such as Iron River fish, in hatchery environments.

In situ survival and growth of three brook trout (Salvelinus fontinalis) strains subjected to acid conditions of anthropogenic origin at the egg and fingerling stages

Tolerance to naturally acidic conditions of a Côte-Nord brook trout (Salvelinus fontinalis) strain (Arseneault strain, presumed acid tolerant) does not appear completely genetically mediated, since this tolerance was not evident when the fish were subject to acid conditions of anthropogenic origin. Three wild brook trout strains, at the egg and fingerling stages, were exposed in the field to waters acidified by atmospheric deposition of anthropogenic origin as well as to natural waters typical of the region. Although egg mortality was significantly higher in acid (61.0-85.6%) than in reference (6.3-20.8%) conditions, no differences between strains were noted. Residual density 1 year after stocking with fingerlings was significantly higher (by 56%) in the reference lake than in the acid lake, but differences between strains did not follow any clear tendency. While overall growth was greater in the acid environment, weight yield was lower except for the Arseneault strain. Variations pertaining to gonadosomatic index and percent mature individuals in both males and females seemed linked more to differences in growth than to chemical conditions. Developing a permanent reintroduction program with the Arseneault strain to counter losses of brook trout populations due to acid precipitation in Québec does not appear justified at this time.

The Genetic Diversity of Native, Stocked, and Hybrid Populations of Brook Trout in the Southern Appalachians

Using mitochondrial DNA (mtDNA) restriction analysis and starch‐gel electrophoresis of the CK‐A2 locus product, we examined genetic variation in 311 brook trout (Salvelinus fontinalis) from 11 native, 5 hatchery‐derived, and 8 hybrid populations in the southern Appalachian Mountains. Native southern Appalachian fish were genetically distinct from hatchery‐derived fish. Southern and hatchery‐derived fish were reliably distinguished based on three mtDNA restriction sites. Native southern haplotypes differed from hatchery‐derived haplotypes by an average of 0.84%. Northern hatchery‐derived haplotypes varied little in mtDNA compared to native southern haplotypes. Introgression of mtDNA haplotypes and the CK‐A2 locus varied among populations, and introgression of allozyme and mtDNA markers was positively correlated. Continued introductions of nonnative strains of brook trout in the southern Appalachians could simplify the genetic structure of native brook trout populations and eliminate unique genotypes.

Growth, Survival, and Vulnerability to Angling of Three Wild Brook Trout Strains Exposed to Different Levels of Angler Exploitation

Abstract It has been suggested that the genetic growth potential of trout may be degraded over time by differential angler harvest of the faster-growing fish of each cohort. To test this hypothesis, young-of-the-year wild brook trout Salvelinus fontinalis from two branches of the Au Sable River and from the East Branch of the Fox River were stocked in three experimental Michigan lakes to determine their relative 2-year growth and survival. Brook trout populations from the Au Sable River are believed to have been exploited more intensively than the population from the East Branch of the Fox River. We found that brook trout from the East Branch Fox River grew significantly faster than fish from either the North Branch or the mainstream Au Sable River. The superior growth of East Branch Fox River brook trout was most evident in Hemlock Lake, where all strains grew best. Mature males were significantly longer and heavier than mature females when data were pooled across strains for each lake, East Branch Fox R...

Survival, Growth, Movement, and Distribution of Two Brook Trout Strains Stocked into Small Adirondack Streams

Abstract Six field trials were conducted in two streams to compare the survival, growth, movement, and distribution of young-of-year Assinica strain and Temiscamie strain brook trout Salvelinus fontinalis 15–91 d after stocking. No consistent differences between strains in recovery after stocking or in growth were detected; however, movement and distribution within streams differed consistently between strains. Approximately four Temiscamie to one Assinica fish moved downstream 2–15 h after stocking. At the conclusion of five trials, the strains were dissimilarly distributed within streams (distribution was not assessed in the sixth trial): a large proportion of Assinica fish were found in the most upstream section of the streams, whereas a large proportion of Temiscamie fish were found in the most downstream section. These differences in movement and distribution may be related to the origins of the strains in large lake systems in Quebec, where spawning occurs in inlet and outlet streams. Assinica fish,...

Performance of Domestic, Hybrid, and Wild Strains of Brook Trout, Salvelinus fontinalis, after Stocking: the Impact of Intra- and Interspecific Competition

Wild and hybrid strains of brook trout, Salvelinus fontinalis, showed better rates of recovery (by angling) and yield (kilograms of fish recovered per kilogram planted) than a domestic strain, during the 2 yr following planting, in six small oligotrophic lakes of the Laurentian Shield. Native brook trout and white sucker, Catostomus commersoni, had a significant impact on planted brook trout. Recovery, percent of increment in weight and yield of each planted strain were inversely correlated with (1) the relative abundance of native brook trout, and (2) the occurrence of white sucker, supporting hypotheses of intra- and interspecific competition. Furthermore, the response variables were also inversely correlated with the number of potential competitors, indicating that the impact of native brook trout and white sucker was additive. The recovery in number of planted trout (both years and all strains) was approximately four times higher in lakes with effectively no competitors than in lakes containing both white sucker and native brook trout; the increase in weight was nearly three times higher, and the yield was more than nine times higher. The performances of planted fish were intermediate in the lake containing only native brook trout as competitor.

Comparative Ecology and Behavior of Domestic, Hybrid, and Wild Strains of Brook Trout, Salvelinus fontinalis, after Stocking

Two years after planting in six small oligotrophic lakes, domestic, hybrid and wild strains of brook trout, Salvelinus fontinalis, used space and food resources in the same way as native trout. Although trout living with or without white sucker, Catostomus commersoni, were similarly spatially distributed, they had different diets, suggesting a feeding niche shift of trout in the presence of sucker; we concluded that this shift is under phenotypic control because each planted strain came from similar genetic backgrounds. Sexual maturity was related to the size of individuals, regardless of the strain, and males matured before females. Almost all males and females were sexually mature in the first fall after stocking except wild females (3.0 and 75% matured during the first and second fall, respectively). Gonadosomatic indices (GSI) of domestic and hybrid females were similar during the first fall, but the GSI of domestic females was significantly higher than that of hybrid and wild strains in the second fail. Mean egg diameters were similar among the three strains during the two falls, but fecundity of domestic females, after correction for size differences, was significantly higher than that of hybrid females which, in turn, was significantly higher than that of wild ones.

Differences in acid tolerance during the early life stages of three strains of brook trout, Salvelinus fontinalis

Brook trout, Salvelinus fontinalis, embryos and fry from three sources (an acidic watershed in Kejimkujik Park at pH 4.7 to 5.3, a neutral watershed at pH 7, a hatchery at pH 7) were exposed separately to lethal and sublethal levels of acidity (pH 7.0, 5.2, 4.7, 4.3, 3.9), beginning at fertilization. Significant differences in mortality between the strains at low pH were observed and these suggested a genetic component to acid tolerance. Mortality in the strain from the acidic watershed was the lowest, followed by the second wild strain. Survival in both wild strains at low pH was much better than survival in hatchery embryos. These differences in survival at sublethal acidity (4.7 to 7.0) were principally the result of high mortality shortly after fertilization. After this period, survival stabilized. Only at pH 4.3 did substantial mortality occur at hatching. The early embryonic stage therefore appears to be the most susceptible to sublethal acid stress in brook trout. Hatchery strain embryos were also introduced at the eyed stage at 213 degree-days. Subsequent survival of this group was better at low pH than that of hatchery embryos introduced at fertilization, thereby indicating an early or cumulative deleterious effect. Higher acidity retarded hatch in all cases. The time to 50% hatch was delayed by 1.2 degree-days with each increase of 1 μM H+.

Comparison of Survival, Emigration, Habitat Use, Marking Mortality, and Growth between Two Strains of Brook Trout in Adirondack Ponds

Abstract Performances of age-0 Assinica and Temiscamie strain brook trout Salvelinus fontinalis were compared in 1985 and 1986, 2-3 months after the fish had been stocked into two drainable ponds located in the Adirondack Mountains of New York. Overall recovery did not differ significantly between strains in three trials when both pond and inlet habitats were considered. Assinica fish emigrated at higher rates in all three trials than Temiscamie fish. In both 1986 trials, approximately 50% of the recovered Assinica brook trout were in the inlet stream, but less than 25% of the recovered Temiscamie brook trout had emigrated upstream. These differences in emigration may indicate habitat preferences of these strains or density-dependent displacement. The Temiscamie strain had higher marking mortality than the Assinica strain; thus, the Assinica strain appeared to be more resistant to the stress of handling. Temiscamie brook trout had significantly higher instantaneous growth rates after stocking than the Ass...

Comparative Survival and Growth of Planted Wild, Hybrid, and Domestic Strains of Brook Trout (Salvelinus fontinalis) in Ontario Lakes

Matched plantings of domestic strain and interstrain hybrid (or wild strain) brook trout (Salvelinus fontinalis) were made annually in nine small Precambrian Shield lakes during 1973–77. Recoveries of planted fish were made by gillnetting and/or angling during 1974–80. In six study lakes, hybrids (and wild strains) were recovered at rates two to four times greater than the domestic strain; in three lakes recoveries were similar. Most domestic strain trout were caught in the year following planting whereas recoveries of hybrids and wild strains were spread over 3–4 yr. Each kilogram of hybrid (or wild) planted yielded 5.6 kg (1.2–12.3); each kilogram of domestic strain planted yielded 0.8 kg (0.2–2.1). Lakes containing only minnows and sticklebacks yielded the highest returns of brook trout; lakes containing competitive species yielded low returns. Rapid growth of brook trout occurred in lakes containing only minnows and sticklebacks; slowest growth was noted in lakes supporting white suckers (Catostomus commersoni). Domestic strain brook trout and the matched hybrid grew at approximately the same rate within a lake and in seven of the nine lakes ate the same food. The performance of the Nipigon × domestic hybrid qualifies it for consideration as a replacement for the domestic brook trout presently planted in Ontario lakes.Key words: planting, brook trout, trout strain, hybrid, Precambrian Shield, survival, stock

Performance of Indigenous, Exotic, and Hybrid Strains of Brook Trout (Salvelinus fontinalis) in Waters of the Adirondack Mountains, New York

Eleven year-classes of wild, domestic, and wild × domestic hybrid strains of brook trout (Salvelinus fontinalis) were stocked in a 0.19-ha Adirondack pond. Comparative survival and growth were assessed upon drainage in early fall. Rearing native wild strains to maturity in a hatchery, or domestic strains in a natural environment, did not consistently or materially affect survival of progeny, suggesting that superior performance of wild strains was largely inherent. Interstrain hybrids of wild × domestic showed survivals equivalent to the wild parents, but hybrids of two Canadian strains gave evidence of heterosis in both survival and net yield. Supplementary observations in other waters also indicated that one strain (Assinica) may be less adaptable to Adirondack conditions than the other (Temiscamie).Key words: brook trout, wild trout, domesticated trout, interstrain hybrid trout, survival, growth, heterosis, hybrid vigor

The effects of season and acute sub-lethal exposure on survival times of brook trout at low pH

Edray strain brook trout were exposed to sub-lethal pH's of 5.0 and 5.8 (H 2SO 4) for 24h or less and the effect on survival times at pH's 3.15 or 3.5 measured. Pronounced behavioral signs of distress occurred at these sub-lethal pH's, but usually disappeared within 1 h of the initial exposure. No change in resistance times due to the pre-treatment was observed. A marked seasonal decline in survival times was obtained between December and February. Heritable differences in acid tolerance of some inbred strains of brook trout were large.

Production of Wild, Domestic, and Interstrain Hybrids of Brook Trout (Salvelinus fontinalis) in Natural Ponds

Hatchery-reared wild and domestic strains of brook trout (Salvelinus fontinalis) were released in natural lakes, and survival and growth estimated at semiannual intervals throughout the life span. Angling was restricted. Four experiments with two year-classes involved three different Adirondack Mountain (New York) wild strains and two domestic strains, a fifth experiment included two wild strains from James Bay, Quebec and a hybrid between one of these (Assinica Lake) and a New York domestic strain. Wild and hybrid strains consistently exhibited greater longevity (5–7 yr) compared with domestic (few recovered after 3 yr). Climax sizes were not much different, except the Domestic × Assinica hybrid that was substantially larger than either of the two parents. Gross production and yield to angling of any given strain cohort was correlated (r = 0.93) and life-span gross production was 50% greater for wild and hybrid groups per unit fish stocked. Biomass stocked per recruit was much larger for domestic strains, and taking this into account, the ratio of gross production to weight stocked was about 6 times greater. Increased costs of rearing nondomesticated strains, if any, must be taken into consideration in an economic evaluation, but use of wild and/or hybrid strains of trout offers significant benefits under management conditions of these experiments.

Comparative Survival of Wild and Domestic Strains of Brook Trout in Streams

Abstract Survival and growth of progeny of domestic, domestic X wild, and wild strains of brook trout (Salvelinus fontinalis) were compared after these trout were released during the fall as fingerlings 9 to 10 months old in selected sections of streams. One group of the wild strain was hatched and reared in the wild. Other groups were hatched and reared in the hatchery. The domestic strain had the highest over-winter survival in three of five streams. In only one stream did the wild strain have the highest over-winter survival. In the four streams investigated during the fall, the wild strain had the highest summer-survival. Survival of the domestic and domestic X wild strains through the summer fishing season was generally too low to evaluate survival of these strains through the second winter. The domestic strain grew most rapidly in the hatchery followed by the domestic X wild strain. This growth advantage was not maintained after release into streams. Brook trout of the domestic strain were harvested...