Abstract
Captive propagation of Pacific salmon is routine, but few captive breeding programs have been conducted to successfully re-establish extirpated wild populations. A captive breeding program for endangered Sakinaw Lake sockeye salmon was established from 84 adults between 2002 and 2005, just prior to extirpation of the wild population. After several years of absence, sockeye salmon released from captivity returned to spawn in Sakinaw Lake in 2010 and in all years thereafter. Freshwater survival rates of released hatchery fry and naturally produced progeny of reintroduced sockeye salmon have not limited abundance of the reintroduced population. In contrast, marine survival rates for Sakinaw sockeye salmon have been <1%, a level that precludes population restoration in the absence of supplementation. Genetic diversity commensurate with the number of parental founders has been maintained in captivity. The 517 adult second-generation captive fish that spawned in Sakinaw Lake in 2011 produced a smolt emigration of almost 28,000 juvenile fish with an effective population size of 132. Allelic richness and gene diversity levels in the smolts were similar to those observed in captivity. This indicates genetic contributions from all or most founding parents have been retained both in captivity and in the nascent reintroduced natural population.
Highlights
Biodiversity in salmonid species is maintained by their metapopulation structure, in which local adaptation to wild environments occurs in spite of gene flow among breeding units occupying the same or different watersheds [1]
Captive breeding can be used to re-establish a natural population that is briefly extirpated from its natural environment, albeit generally with an associated reduction in genetic diversity compared with the original wild population [8]
Between 2006 and 2009, inclusive, zero or one sockeye salmon returned to Sakinaw Lake and no spawning occurred at Ouillet hatchery
Summary
Biodiversity in salmonid species is maintained by their metapopulation structure, in which local adaptation to wild environments occurs in spite of gene flow among breeding units occupying the same or different watersheds [1]. Maintenance of genetic diversity in the natural environment was a cornerstone of the Wild Salmon. Captive breeding can be used to re-establish a natural population that is briefly extirpated from its natural environment, albeit generally with an associated reduction in genetic diversity compared with the original wild population [8]. The reduction in diversity due to a small number of potentially related founders and an increase in inbreeding during captivity may be exacerbated upon reintroduction to the wild, while natural population size remains small [9]. All three federal captive breeding programs established for endangered salmon populations in Canada
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