By Thomas P. Quinn
Fisheries Research, Volume 18, Issues 1-2, Biological Interactions of Natural and Enhanced Stocks of Salmon, October 1993, Pages 29-44, ISSN 0165-7836, DOI: 10.1016/0165-7836(93)90038-9.

This paper reviews studies on the patterns of straying of adult salmonids from their river or hatchery of origin, with emphasis on Pacific salmon. The prevalence of straying varies greatly among populations. In general, introduced (i.e. non-native) populations and salmon displaced from their rearing site for release stray more than native salmon and those reared and released on-site. Evidence that standard hatchery practices increase the tendency of salmon to stray is equivocal but releases of salmon at a different season from the normal migration period can increase straying. Estimates of straying vary greatly between hatcheries and rivers, so general statements on straying proportions have minimal biological significance. Straying between hatcheries and spawning grounds gives cause for concern because there is evidence that the offspring of hatchery-produced salmon may be less viable than those from local wild fish. The impact of straying on local gene pools depends not only on the prevalence of straying but on the degree of assortative mating and survival differential between populations. At present, fundamental gaps in our understanding of the genetic and environmental factors that influence straying hinder accurate prediction of the levels and consequences of straying.

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