Outbreeding depression in hybrids between odd-and even-broodyear pink salmon

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Fewer F2 hybrids between even- and odd-broodline pink salmon (Oncorhynchus gorbuscha), which are lines that are genetically isolated by their strict two-year life cycle, survived than did F2 controls, indicating outbreeding depression. Cryopreserved sperm of 40 broodyear 1990 males and of 40 broodyear 1991 males fertilized equal subsamples of eggs from 40 broodyear 1992 females. Return rates of F1 hybrids (1.73%) and controls (1.63%) in 1994 did not differ significantly (P=0.30). F2 hybrid and control crosses were made from 40 males and 40 females selected at random from each return group. Offspring were differentially marked and released. In 1996, returns differed significantly (P=0.011) between hybrids (n=34, 0.34%) and controls (n=44, 0.42%). The low rate of return of the control fish was similar to the measured return of a much larger group of tagged Auke Creek pink salmon, and probably not an artifact of the experiment. Although no increase in fluctuating asymmetry of paired meristic counts was observed in either F1or F2 hybrids, size and some meristic counts of hybrids exceed measurements of controls, suggesting heterosis for those traits. The observations of decreased survival in F2 hybrids confirm previous work [Gharrett, A.J., Smoker, W.W., 1991. Two generations of hybrids between even- and odd-year pink salmon (O. gorbuscha). Canadian Journal of Fisheries and Aquatic Science 48(9) 1744–1749]. Although genetic divergence between pink salmon broodlines is large and outbreeding depression might be expected in such unlikely hybrids, the results document the occurrence of outbreeding depression in salmon and signal caution in making management and aquacultural decisions that may create the possibility of outbreeding depression in self-sustaining or cultured populations.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Outbreeding depression in hybrids between odd-and even-broodyear pink salmon
Series title Aquaculture
DOI 10.1016/S0044-8486(98)00480-3
Volume 173
Issue 1-4
Year Published 1999
Language English
Publisher Elselvier
Contributing office(s) Western Fisheries Research Center
Description 13 p.
First page 117
Last page 129
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