Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8673
Title: Rearing strategies alter patterns of size-selective mortality and heritable size variation in steelhead trout (Oncorhynchus mykiss)
Author: B. A. Berejikian, Jeffrey J. Hard, C. P. Tatara, Donald M. Van Doornik, P. Swanson, Donald A. Larsen
Publication Year: 2016
Journal: Canadian Journal of Fisheries and Aquatic Sciences
Volume: 74
Issue: 2
Pages: 273-283
DOI: 10.1139/cjfas-2016-0175

Domestication selection in cultured anadromous salmonids is widely hypothesized to result from selection favoring rapid growth rate and correlated physiological or behavioral traits. Steelhead trout (Oncorhynchus mykiss) were reared under two different regimes: high food ration for one year (S1; typical strategy) or low ration for two years (S2) and subjected to a seawater challenge during the corresponding the spring outmigration period. The S1 smolts were smaller, suffered greater seawater challenge mortality (23.9% compared to 0.7% for the S2 smolts) that was significantly and negatively related to body size. Overall, heritability for challenge mortality was low (0.002; 95% credible interval: 0.001-0.589). Heritability for body size (reflecting growth rate within each rearing treatment) was similar for the two treatments during the parr stage (fork length: S1 = 0.181, S2 = 0.245; mass: S1 = 0.372; S2 = 0.447), but higher for the S1 treatment during the smolt stage for length (S1 = 0.212, S2 = 0.002) and body mass (S1 = 0.145, S2 = 0.015). General linear models confirmed strong family effects for both traits and significant family by environment interactions for parr mass and smolt length, indicating significant phenotypic plasticity. The results are consistent with the hypothesis that size-selective mortality in steelhead trout is more likely to occur where there is insufficient growth opportunity for smolts to achieve body size thresholds for smoltification (S1 treatment) and may be alleviated by an additional year of culture. A genetic response to selection in the S1 treatment is plausible, and may affect fitness in the natural environment through effects on correlated traits.


The manuscript estimates the effects of hatchery reararing strategies on size-selective mortality and heritability of growth rate

Theme: Recovery and rebuilding of marine and coastal species
Foci: Evaluate the effects of artificial propagation on recovery, rebuilding and sustainability of marine and anadromous species.
Official Citation:

Berejikian, B.A., Hard, J.J., Tatara, C.P., Van Doornik, D.M., Swanson, P., and Larsen, D.A. Rearing strategies alter patterns of size-selective mortality and heritable size variation in steelhead trout (Oncorhynchus mykiss). Canadian Journal of Fisheries and Aquatic Sciences. 74: 273-283