Maintenance of Genetic Diversity in Natural Spawning of Captively-Reared Endangered Sockeye Salmon, Oncorhynchus nerka

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.

The Productivity and Viability of Snake River Sockeye Salmon Hatchery Adults Released into Redfish Lake, Idaho

“…) and Sakinaw Lake, British Columbia (egg‐to‐smolt survival range, 0.1% to 6%, and SAR range, 0 to 0.8%: Withler et al. ; COSEWIC ).…”

“…; Withler et al. ). Captive broodstock programs are distinct from other hatchery programs in that fish remain in a hatchery environment throughout their entire life cycle (Flagg and Mahnken ; Miller and Kapuscinski ; Berejikian et al.…”

“…; Withler et al. ). The variability in outcomes can be complex and multifaceted depending on species, available habitat, geographic location, phenotypic and behavioral traits, and approach.…”

“…Captive broodstock programs have been established in both Europe and North America as a safety net to conserve genetic diversity and reduce the extinction probability of highly imperiled fish species and/or populations (Carr et al 2004;Cooper et al 2009;Withler et al 2011;Saltzgiver et al 2012;Osborne et al 2013;Withler et al 2014). Captive broodstock programs are distinct from other hatchery programs in that fish remain in a hatchery environment throughout their entire life cycle (Flagg and Mahnken 1995;Miller and Kapuscinski 2003;Hebdon et al 2004) and are genetically managed to avoid inbreeding depression and unintended selection (Kozfkay et al 2008;Sturm et al 2009;Fisch et al 2012Fisch et al , 2015Kalinowski et al 2012;Conrad et al 2013;O'Reilly and Kozfkay 2014).…”

“…In some cases, hatchery adults have been unsuccessful at spawning after release (Carr et al 2004;Griffiths et al 2011) or have been able to successfully spawn but have had negative impacts on reproductive fitness of natural populations (Araki et al 2007(Araki et al , 2008Christie et al 2014). In other cases, salmon reintroductions have produced demographic increases (Berejikian et al 2009;Hess et al 2012;Withler et al 2014). The variability in outcomes can be complex and multifaceted depending on species, available habitat, geographic location, phenotypic and behavioral traits, and approach.…”