Supportive breeding boosts natural population abundance with minimal negative impacts on fitness of a wild population of Chinook salmon

Abstract

While supportive breeding programmes strive to minimize negative genetic impacts to populations, case studies have found evidence for reduced fitness of artificially produced individuals when they reproduce in the wild. Pedigrees of two complete generations were tracked with molecular markers to investigate differences in reproductive success (RS) of wild and hatchery-reared Chinook salmon spawning in the natural environment to address questions regarding the demographic and genetic impacts of supplementation to a natural population. Results show a demographic boost to the population from supplementation. On average, fish taken into the hatchery produced 4.7 times more adult offspring, and 1.3 times more adult grand-offspring than naturally reproducing fish. Of the wild and hatchery fish that successfully reproduced, we found no significant differences in RS between any comparisons, but hatchery-reared males typically had lower RS values than wild males. Mean relative reproductive success (RRS) for hatchery F1 females and males was 1.11 (P = 0.84) and 0.89 (P = 0.56), respectively. RRS of hatchery-reared fish (H) that mated in the wild with either hatchery or wild-origin (W) fish was generally equivalent to W × W matings. Mean RRS of H × W and H × H matings was 1.07 (P = 0.92) and 0.94 (P = 0.95), respectively. We conclude that fish chosen for hatchery rearing did not have a detectable negative impact on the fitness of wild fish by mating with them for a single generation. Results suggest that supplementation following similar management practices (e.g. 100% local, wild-origin brood stock) can successfully boost population size with minimal impacts on the fitness of salmon in the wild.

Two Rivers: The Politics of Wild Salmon, Indigenous Rights and Natural Resource Management

“…The study used DNA from all returning adults collected over a 13-year period to track parents and their offspring, to determine how successful hatchery fish were at mating in the wild when compared to wild fish. This success was connected, by Hess and her team [67], to the fact that tribal hatcheries were able to limit genetic changes during captivity, by steadily incorporating wild individuals adapted to local environmental conditions into the captive stock each year [67]. A key finding in this study was that hatchery-origin fish that spawned naturally with a wild fish had an equivalent reproductive success as two wild fish.…”

“…Hess and her team were therefore able to suggest that Chinook salmon reared for a single generation in this supplementation hatchery did not reduce the fitness of wild fish. Similarly, productivity of two hatchery fish spawning naturally was not significantly lower than for two wild fish [67].…”

“…Tribal hatcheries, however, claim to be able to produce salmon with higher reproduction rates [65]. In an early study, undertaken by molecular biologists, members of CRITFC and the Nez Perce tribe's Johnson Creek Artificial Propagation Enhancement Project, researchers found that hatchery-reared salmon spawned with wild salmon, had the same reproductive success as salmon left to spawn in the wild, in the same generation [67]. The study used DNA from all returning adults collected over a 13-year period to track parents and their offspring, to determine how successful hatchery fish were at mating in the wild when compared to wild fish.…”

Loss of Genetic Integrity in Hatchery Steelhead Produced by Juvenile‐Based Broodstock and Wild Integration: Conflicts in Production and Conservation Goals

“…From a genetics perspective, a common objective is to create broodstocks that reduce consequences such as reductions in effective population size (N e ) and changes in genetic variation compared with the wild populations they supplement (Hulett et al 2004;Mobrand et al 2005). An increasingly popular method of broodstock management designed to meet these goals is supplementation with hatchery fish produced by genetically integrated broodstocks (Araki et al 2007;Paquet et al 2011;Christie et al 2012;Hayes et al 2012;Hess et al 2012). In this method, prescribed proportions of wild-born fish (e.g., Mobrand et al 2005;Moyer et al 2007;Hess et al 2012), or a range of proportions (i.e., Hedrick et al 2000;Eldridge and Killebrew 2008), are mated in captivity with other wild or hatchery fish and their offspring are allowed to spawn in the wild.…”

Habitat protection for sensitive species: Balancing species requirements and human constraints using bioindicators as examples

“…Now, sometimes hatchery fish produce more offspring that reach adulthood than wild salmon in the same rivers reproducing naturally [16]. The Columbia River Basin once had the largest salmon runs in the world (10 -16 million fish), but these have decreased to about a million upriver salmon [9].Chinook run up river spring, summer and fall.…”