Genetic, environmental and interaction effects on the incidence of jacking in Oncorhynchus tshawytscha (chinook salmon)

Abstract

Jacking in chinook salmon, Oncorhynchus tshawytscha, is defined as sexual maturation of males after at least 1 year in sea water, occurring 1 year prior to any of the females of the same cohort. A breeding experiment was carried out with jack and non-jack sires nested within six dams. The resulting 12 families were reared under two different temperatures for the first part of their lives to test for the effect of early developmental acceleration on jacking rates. Significant sire age (jack vs.non-jack), dam and environment (water temperature) effects were found for the incidence of jacking. Significant genotype-by-environment interactions were also found, indicating that accelerated early development does not increase jacking rates uniformly across all genotypes.There were no significant correlations between mean family growth-and size-related variables and the observed jacking rates. Heritability estimates based on intra-dam sire-offspring regressions were 0.48 (± 0.24) and 0.32 (± 0.14) for the accelerated and non-accelerated family groups, respectively. The results of sib-analysis heritability calculations indicated large dominance effects or sex linkage. The genetic component to jacking found in this study for chinook salmon was greater than has been generally reported for age of first maturation in salmonids.

Genetic variation in threshold reaction norms for alternative reproductive tactics in male Atlantic salmon,Salmo salar

“…Firstly, the incidence of male parr maturity differed among pure-and mixed-population crosses in a common environment, indicating that there is a genetic basis to the probability with which a male adopts the mature parr phenotype. This finding is consistent with previous reports of a genetic basis for alternative reproductive tactics in salmonid fish (Glebe & Saunders 1986;Heath et al 1994;Garant et al 2003). Secondly, among-cross differences in growth-rate switch points indicate the presence of amongpopulation genetic variability in threshold reaction norms for alternative male phenotypes, suggesting that thresholds may vary among genotypes within populations (Hazel et al 1990) and respond to natural and anthropogenic selection.…”

A novel method for estimating heritability using molecular markers

“…Houle, 1993). The estimate of heritability for jacking (0.67) is in accordance with previous estimates of 0.73-1.86 obtained using sib analyses in a conventional quantitative genetic design for this same population of chinook salmon (Heath et al, 1994). Because sireoffspring regression analysis indicated heritabilities of 0.32-0.77, large nonadditive genetic effects are probably present for this trait in this population (Heath et al, 1994).…”

“…The methods used for DNA extraction and fingerprinting are provided by Heath et al (1994). Briefly, liver or testes samples were taken from each fish for DNA extraction according to the protocol given by Devlin et al (1991).…”

“…For Southern analysis, 3 g of DNA from each individual were digested overnight with the restriction endonuclease HaeIII, size fractionated by gel electrophoresis and transferred to 20 25 cm nylon membranes. The membranes were hybridized with two probes: OtSL1, a chinook salmon hypervariable probe developed by Heath et al (1994) using directed amplification of minisatellite region DNA (DAMD; Heath et al 1993), and Ssa1, a highly variable single-locus probe (SLP) developed for Atlantic salmon (Bentzen & Wright, 1993) and found suitable for use with chinook salmon. Nylon membranes were first hybridized with random-primed radiolabelled OtSL1 probe and exposed to X-ray film for 1-2 days with an intensifying screen at 70°C.…”

"Research to Improve the Efficacy of Captive Broodstock Programs and Advance Hatchery Reform Throughout the Columbia River Basin." [from the Abstract], 2008-2009 Progress Report.

“…This is in part because they are not genetically distinct and because the interplay between genetic and environmental factors determines the 'decision' whether or not an individual will mature early. Evidence for strong heritability in age-at-maturity comes from quantitative genetic studies (Hankin et al 1993;Heath et al 1994;Heat et al 2002) and measures at the population level (Hard et al 1985, Appleby et al 2003. Physiological traits mediated by environmental conditions (e.g., body size, fatness), can trigger early male maturation (Vøllestad et al 2004;Shearer et al 2008).…”