Genetic variation in mortality of chinook salmon, Oncorhynchus tshawytscha (Walbaum), challenged with high water temperatures

Low levels of heterozygosity can have detrimental effects on life history and growth characteristics of organisms but more subtle effects such as those on trade-offs of expensive tissues and morphological laterality, especially of the brain, have not been explicitly tested. The objective of the current study was to investigate how estimated differences in heterozygosity may potentially affect brain-to-body trade-offs and to explore how these heterozygosity differences may affect differential brain growth, focusing on directional asymmetry in adult Chinook salmon ( Oncorhynchus tshawytscha ) using the laterality and absolute laterality indices. Level of inbreeding was estimated as mean microsatellite heterozygosity resulting in four ‘inbreeding level groups’ (Very High, High, Medium, Low). A higher inbreeding level corresponded with a decreased brain-to-body ratio, thus a decrease in investment in brain tissue, and also showed a decrease in the laterality index for the cerebellum, where the left hemisphere was larger than the right across all groups. These results begin to show the role that differences in heterozygosity may play in differential tissue investment and in morphological laterality, and may be useful in two ways. Firstly, the results may be valuable for restocking programmes that wish to emphasize brain or body growth when crossing adults to generate individuals for release, as we show that genetic variation does affect these trade-offs. Secondly, this study is one of the first examinations to test the hypothesized relationship between genetic variation and laterality, finding that in Chinook salmon there is potential for an effect of inbreeding on lateralized morphology, but not in the expected direction.

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Genetic variation in freshwater survival and growth of chinook salmon (Oncorhynchus tshawytscha)

Aquaculture ◽

10.1016/0044-8486(87)90344-9 ◽

1987 ◽

Vol 64 (2) ◽

pp. 85-96 ◽

Cited By ~ 30

Author(s):

R.E. Withler ◽

W.C. Clarke ◽

B.E. Riddell ◽

H. Kreiberg

Keyword(s):

Genetic Variation ◽

Chinook Salmon ◽

Oncorhynchus Tshawytscha ◽

Survival And Growth

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Genetic variation in survival of chinook salmon (Oncorhynchus tshawytscha) alevins exposed to an unidentified agent of mortality

Genome ◽

10.1139/g87-143 ◽

1987 ◽

Vol 29 (6) ◽

pp. 839-845 ◽

Cited By ~ 5

Author(s):

R. E. Withler

Keyword(s):

Genetic Variation ◽

Chinook Salmon ◽

Oncorhynchus Tshawytscha ◽

Mean Value ◽

Unknown Etiology ◽

Maternal Allele ◽

Paternal Effects ◽

Time To Death ◽

The Mean ◽

Family Survival

Mortality of an unknown etiology occurs after hatching and before emergence among Harrison River chinook salmon (Oncorhynchus tshawytscha) alevins incubated in the Chehalis River Hatchery, British Columbia. Inter- and intra-stock genetic variation for alevin survival and time to death was investigated at Chehalis Hatchery in factorial crosses among chinook salmon from the Harrison and Capilano rivers. Alevin survival by family ranged from 0 to 100%, with a mean value of 35.2%. The mean family survival of pure Harrison alevins (13.0%) was significantly lower than that of Capilano alevins (64.1%). For the Harrison stock, estimates of the heritability of survival were 1.05 ± 0.62 (sire component) and 0.03 ± 0.07 (dam component). For the Capilano stock, the corresponding estimates were 0.79 ± 0.53 and 0.80 ± 0.54. Family means of time to death ranged from 7.5 to 48 days after exposure to mortality-inducing agents. The mean times to death for pure Harrison (15.3 days) and Capilano (21.8 days) families were not significantly different. Sire and dam component heritability estimates for time to death were high for the Harrison stock (1.39 ± 0.87 and 0.71 ± 0.46) but low for the Capilano stock (0.06 ± 0.11 and 0.17 ± 0.18). Values of survival and time to death for the reciprocal interstock hybrid alevins generally fell between those of the parental stocks. Neither survival nor time to death differed significantly between the reciprocal hybrids, but both traits were more strongly influenced by sire than by dam. The possibility of asynchronous paternal and maternal allele activation during embryonic development was proposed as an explanation for the strong paternal effects observed in this study. Key words: Oncorhynchus, salmon, heritability, mortality.

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Differences in Enzyme Frequency and Body Morphology among Three Juvenile Life History Types of Chinook Salmon (Oncorhynchus tshawytscha) in the Nanaimo River, British Columbia

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f84-125 ◽

1984 ◽

Vol 41 (7) ◽

pp. 1070-1077 ◽

Cited By ~ 55

Author(s):

L. M. Carl ◽

M. C. Healey

Keyword(s):

Genetic Variation ◽

Life History ◽

Chinook Salmon ◽

Oncorhynchus Tshawytscha ◽

High Salinity ◽

Salt Water ◽

Salinity Adaptation ◽

Significant Excess ◽

Body Morphology ◽

Seaward Migration

Chinook salmon (Oncorhynchus tshawytscha), in the Nanaimo River and elsewhere, exhibit three juvenile life history types characterized by different ages at seaward migration. One type migrates to sea immediately after emergence from the spawning gravel and rears in high-salinity estuarine habitats, a second migrates seaward after rearing for about 2 mo in freshwater, and a third type after rearing for a year in freshwater. Nanaimo River chinook were polymorphic at 10 of 31 loci examined electrophoretically. The frequency of allozymes differed significantly among the three life history types at 4 of the 10 loci. A significant deficiency of heterozygotes at the locus for PMI-2 characterized juveniles that reared in estuarine habitats. Fry that died on transfer to salt water in the laboratory had a significant excess of PMI-2 heterozygotes, suggesting that this locus may be associated with salinity adaptation. The three life history types also differed significantly in body morphology. Fish that reared in the estuary had slimmer bodies, smaller heads, and shorter fins than those that reared in the river. Those that spent a year in freshwater had the largest heads, deepest bodies, and longest fins. These observations corroborate the hypothesis that the three life history types represent genetically isolated subpopulations that appear to be physically adapted to their rearing environment. Current plans to increase the numbers of chinook available to commercial and recreational fishermen through artificial propagation of chinook must be made compatible with this degree of genetic variation.

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Genetic Variation within and Between Domesticated Chinook Salmon, Oncorhynchus tshawytscha, Strains and their Progenitor Populations

Environmental Biology of Fishes ◽

10.1023/b:ebfi.0000022891.83210.2e ◽

2004 ◽

Vol 69 (1-4) ◽

pp. 371-378 ◽

Cited By ~ 16

Author(s):

Ji Eun Kim ◽

Ruth E. Withler ◽

Carol Ritland ◽

Kimberly M. Cheng

Keyword(s):

Genetic Variation ◽

Chinook Salmon ◽

Oncorhynchus Tshawytscha

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Relationships between heterozygosity, allelic distance (d2), and reproductive traits in chinook salmon, Oncorhynchus tshawytscha

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f01-192 ◽

2002 ◽

Vol 59 (1) ◽

pp. 77-84 ◽

Cited By ~ 40

Author(s):

Daniel D Heath ◽

Colleen A Bryden ◽

J Mark Shrimpton ◽

George K Iwama ◽

Joanne Kelly ◽

...

Keyword(s):

Genetic Variation ◽

Chinook Salmon ◽

Regression Models ◽

Oncorhynchus Tshawytscha ◽

Gonadosomatic Index ◽

Reproductive Traits ◽

Reproductive Fitness ◽

Egg Survival ◽

Allele Size ◽

Multivariate Relationships

Correlations of various measures of individual genetic variation with fitness have been reported in a number of taxa; however, the genetic nature of such correlations remains uncertain. To explore this, we mated 100 male and 100 female chinook salmon (Oncorhynchus tshawytscha) in a one-to-one breeding design and quantified reproductive fitness and allocation (male gonadosomatic index, GSI; female fecundity; egg size; egg survival). Each fish was scored for allele size at seven microsatellite loci. We applied univariate and multivariate regression models incorporating two genetic variation statistics (microsatellite heterozygosity and squared allelic distance, d2) with reproductive parameters. The majority of the relationships were found to be nonsignificant; however, we found significant, positive, univariate relationships for fecundity and GSI (25% of tests) and significant, multivariate relationships at individual loci for all four traits (13% of tests). One microsatellite locus, Omy207, appeared to be closely associated with reproductive fitness in female chinook salmon (but not male), based on the multivariate analysis. Although direct tests for overdominance versus inbreeding effects proved inconclusive, our data are consistent with the presence of both inbreeding (general) and overdominance (local) effects on reproductive traits in chinook salmon.

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