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Lake trout exhibit substantial life history variation associated with variation in climatic and biotic variables. To assess the environmental and genetic influences on lake trout life history traits, eggs were collected from two lakes in Algonquin Park, Ontario, Lake Opeongo and Louisa Lake, with contrasting ecotypes and forage bases. Eggs from both populations and interpopulation hybrids (Lake Opeongo females × Louisa Lake males) were raised to maturity in a common controlled environment. There was evidence of a genetic basis to life history variation between ecotypes. Hatchery-reared lake trout from Louisa Lake were found to have a faster prematuration growth rate and earlier age and smaller size at maturation than Lake Opeongo lake trout, whereas Lake Opeongo lake trout had greater postmaturation growth rates. Most of the life history traits of hybrids were intermediate between those of the parent populations. These differences were also consistent with reported differences on these populations in the field. Despite differences in maturation and body size, reproductive investment did not differ significantly among the hatchery-reared populations. There was also evidence of phenotypic plasticity in growth (juvenile and adult) and age at maturity. For fish originating from each lake, hatchery-raised fish showed higher prematuration growth rates and younger ages at maturity than did wild fish. Hatchery-reared fish from Louisa Lake were projected to attain asymptotic sizes nearly 50% larger than those of their wild counterparts. These data provide evidence that wild lake trout populations exhibit a plastic response to resource limitation. The combined results of this study indicate that lake trout life history characteristics are driven by both genetic and environmental influences, which should be incorporated into current life history models and used in making management decisions. [ABSTRACT FROM AUTHOR]

Rainbow trout Oncorhynchus mykiss native to the Athabasca River of the Arctic Ocean drainage differed at several allozyme loci from rainbow trout and anadromous steelhead populations in the adjacent Fraser River and Columbia River drainages. A dendrogram of genetic distances suggested that the rainbow trout from the Athabasca River drainage are genetically distinct from other inland and coastal rainbow trout and steelhead. Principal component analysis of meristic data supported the allozyme analysis and indicated two main groupings, inland and coastal, that both were distinct from the Athabasca fish. The Athabasca rainbow trout appear to have been reproductively isolated for at least 64,000 years, since the recession of the early-Wisconsin glaciation, possibly in an inland refuge in southwest Alberta. [ABSTRACT FROM AUTHOR]

We investigated effects of starvation on acid tolerance of young-of-year smallmouth bass Micropterus dolomieui in the laboratory. Juvenile smallmouth bass, held under simulated winter conditions for up to 5 months, experienced losses in ash-free dry weight of up to 30%. However, consecutive tests failed to demonstrate any decline in the short-term (≤7 d) tolerance of these fish for pH levels in the range from 3.0 to 4.5. We discuss the implications of these findings for northern populations where young-of-year fish experience significant winter starvation, followed by short-term exposure to low pH in spring. Calcium and sodium concentration of the water and fish body size (fork length) were all positively related to acid tolerance. A doubling of fork length increased survival time at any pH by 100%. At pH 3.0, a doubling of calcium concentration increased survival time by 13% and at pH 4.0 it increased survival time by 50%. Over the pH range 3.75 to 4.0, a doubling of sodium concentration increased survival time by 8%. The strong effect offish body size on acid tolerance should be recognized and controlled in future acid tolerance experiments. It should be taken into account when laboratory tolerance estimates are used to assess the susceptibility of wild populations to acid stress. [ABSTRACT FROM AUTHOR]

In an attempt to distinguish between parr of ouananiche (freshwater) and those of anadromous Atlantic salmon Salmo salar, we undertook a study of meristic and morphometric variation among populations from rivers along the Quebec north shore of the Gulf of St. Lawrence. We sampled parr from six locations in 1984; two 1983 samples were used to estimate year-to-year variation in the Watshishou River. Based on the characters examined, no practical method was found for distinguishing between the two types of parr. Morphologically, ouananiche and anadromous parr exhibited significant heterogeneity and could be classified according to origin by discriminant analysis with 71.0-84.6% accuracy. Very little variation in meristic characters was evident among the populations examined. [ABSTRACT FROM AUTHOR]

We used quinacrine hydrochloride and chromomycin A3 staining techniques to examine chromosome-banding polymorphisms in lake trout Salvelinus namaycush from seven wild populations and two hatchery stocks from the Great Lakes region. Although considerable variation in the number of bands occurred among individuals examined by both staining techniques, banding patterns were constant for all cells of a given individual. The populations were differentiated into three groups on the basis of the number of chromomycin A3 bands: a group from the northern shores of Lakes Superior and Huron and the inland lakes north of Lake Superior; a group from the southern shore of Lake Superior; and a group that comprised one wild population and one hatchery stock from Wyoming that were both originally transplanted from a Lake Michigan stock. Each population within these three groups had a unique distribution of chromomycin A3 bands on specific chromosomes. Results for a given population were consistent when sampled for two consecutive years. The populations were very similar in the frequency of Q-band (quinacrine-stained) variants except for one polymorphism found in the Michipicoten Island, Ontario, population and another polymorphism, which was rare in the Seneca Lake, New York, population. The cytogenetic results were compared with allozyme results from the same populations. The populations were similarly differentiated by both the allozyme and cytogenetic data. [ABSTRACT FROM AUTHOR]

Rainbow trout Oncorhynchus mykiss native to the Athabasca River of the Arctic Ocean drainage differed at several allozyme loci from rainbow trout and anadromous steelhead populations in the adjacent Fraser River and Columbia River drainages. A dendrogram of genetic distances suggested that the rainbow trout from the Athabasca River drainage are genetically distinct from other inland and coastal rainbow trout and steelhead. Principal component analysis of meristic data supported the allozyme analysis and indicated two main groupings, inland and coastal, that both were distinct from the Athabasca fish. The Athabasca rainbow trout appear to have been reproductively isolated for at least 64,000 years, since the recession of the early-Wisconsin glaciation, possibly in an inland refuge in southwest Alberta. [ABSTRACT FROM AUTHOR]

Inheritance patterns of randomly amplified polymorphic DNA (RAPD) phenotypes were tested in 13 full-sib families of lake trout Salvelinusnamaycush. Single-pair matings of parents with known phenotypes weremade, and up to 20 progeny of each mating were used to test inheritance patterns. Seven RAPD primers amplified 13 polymorphic bands. Withthe exception of one family, expected segregation ratios for dominant Mendelian genetic traits were observed. Our results support previously reported findings that RAPD markers can be considered Mendelian traits and therefore could be used for analysis of genetic population structure. [ABSTRACT FROM AUTHOR]

In the male trout there is a difference in the quinacrine banding and C-banding patterns between the two homologs of the second largest chromosome pair. This chromosome is the only large submetacentric in the karyotype, making it easy to identify and suggesting that the sex chromosomes have become differentiated since the time of tetraploidization. In males one homolog has a medium-to-large quinacrine bright heterochromatic band on the end of the short arm, while the other lacks it completely. In females both homologs have medium-to-large quinacrine bright heterochromatic bands. Approximately half the progeny from every lake trout cross studied and half the eggs from every lake trout population examined were heteromorphic for a difference in this chromosome band. Results from sexed fish, reciprocal F1 hybrids between brook trout and lake trout, and gynogenetic haploids are all consistent with the interpretation that chromosome 2 is the sex chromosome. These results suggest that the addition of heterochromatin to the X can be the first step in the inhibition of crossing over between the X and Y chromosomes required for sex chromosome differentiation.

Chromosome banding patterns obtained by silver staining (Ag-NORs) were analyzed in three species of Salmo (rainbow, brown trout, and Atlantic salmon) and three species of Salvelinus (brook trout, lake trout, and arctic char). In rainbow trout and Atlantic salmon the Ag-NORs were found at the secondary constrictions of a single chromosome pair, while in brown trout the Ag-NORs were found on the short arms of one or two of the two longest subtelocentric or acrocentric chromosome pairs. The location of the Ag-NORs was multichromosomal in the three Salvelinus species, occurring on one or both members of four to six different chromosome pairs in different individuals. The Ag-NOR sites were on the short arms of some acrocentric pairs and at the telomeres of other acrocentric pairs and one or two metacentric pairs. Chromomycin A3 positive bands were found at the same sites as the Ag-NORs in all species. In the species with multichromosomal location of Ag-NORs, polymorphisms in the size and location of the NORs were extremely common, so that almost every individual fish had a different pattern of Ag-NOR sites.