Estimates of Natural Selection in a Salmon Population in Captive and Natural Environments

Conservation Biology Division, Northwest Fisheries Science Center, 2725 Montlake Boulevard E. Seattle, WA 98112, USA.
Conservation Biology (Impact Factor: 4.17). 07/2008; 22(3):783-94. DOI: 10.1111/j.1523-1739.2008.00965.x
Source: PubMed


Captive breeding is a commonly used strategy for species conservation. One risk of captive breeding is domestication selection—selection for traits that are advantageous in captivity but deleterious in the wild. Domestication selection is of particular concern for species that are bred in captivity for many generations and that have a high potential to interbreed with wild populations. Domestication is understood conceptually at a broad level, but relatively little is known about how natural selection differs empirically between wild and captive environments. We used genetic parentage analysis to measure natural selection on time of migration, weight, and morphology for a coho salmon (Oncorhynchus kisutch) population that was subdivided into captive and natural components. Our goal was to determine whether natural selection acting on the traits we measured differed significantly between the captive and natural environments. For males, larger individuals were favored in both the captive and natural environments in all years of the study, indicating that selection on these traits in captivity was similar to that in the wild. For females, selection on weight was significantly stronger in the natural environment than in the captive environment in 1 year and similar in the 2 environments in 2 other years. In both environments, there was evidence of selection for later time of return for both males and females. Selection on measured traits other than weight and run timing was relatively weak. Our results are a concrete example of how estimates of natural selection during captivity can be used to evaluate this common risk of captive breeding programs.
Resumen: La reproducción en cautiverio es una estrategia usada comúnmente para la conservación de especies. Un riesgo de la reproducción en cautiverio es la selección por domesticación—la selección de atributos que son ventajosos en cautiverio pero deletéreos en el medio silvestre. La selección por domesticación es de interés particular para especies que han sido reproducidas en cautiverio por muchas generaciones y que tienen un alto potencial de entrecruzarse con poblaciones silvestres. La domesticación es entendida conceptualmente a nivel general, pero se conoce poco sobre como difiere empíricamente la selección natural entre ambientes silvestres y cautivos. Utilizamos análisis parental genético para medir la selección natural sobre el tiempo de migración, peso y morfología de una población de salmón Oncorhynchus kisutch que fue subdividida en componentes cautivos y naturales. Nuestra meta fue determinar si la selección natural que actúa sobre los atributos que medimos difiere significativamente entre los ambientes cautivos y naturales. Para machos, los individuos más grandes fueron favorecidos tanto en los ambientes cautivos como en los naturales, en todos los años del estudio, lo que indica que la selección de estos atributos en cautiverio era similar a la del medio silvestre. Para hembras, la selección de peso fue significativamente mayor en el ambiente natural que en el cautivo en 1 año y similar en los 2 ambientes en los otros dos años. En ambos ambientes hubo evidencia de selección de un mayor tiempo de retorno tanto para machos como hembras. La selección de los atributos medidos distintos al peso y el tiempo de corrida fue relativamente débil. Nuestros resultados son un ejemplo concreto de cómo las estimaciones de selección natural durante el cautiverio pueden ser utilizadas para evaluar este riesgo común en los programas de reproducción en cautiverio.

Download full-text


Available from: Jeffrey J. Hard, Jul 07, 2015
  • Source
    • "While the first step in the process has been successfully accomplished, as eggs taken from Devils Hole have been hatched in captivity, serious obstacles remain before releases of pupfish can occur. Unfortunately, the longer that pupfish remain in captivity before being returned to the wild, the greater the likelihood of selection for domestication and loss of behaviors needed to survive in the wild (Ford et al., 2008; Frankham, 2008; Kelley, Magurran & Macías García, 2006; Snyder et al., 1996). Avoidance of domestication will be a key priority in managing the captive population (LH Simons, pers. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The Devils Hole pupfish is restricted to one wild population in a single aquifer-fed thermal pool in the Desert National Wildlife Refuge Complex. Since 1995 the pupfish has been in a nearly steady decline, where it was perched on the brink of extinction at 35-68 fish in 2013. A major strategy for conserving the pupfish has been the establishment of additional captive or "refuge" populations, but all ended in failure. In 2013 a new captive propagation facility designed specifically to breed pupfish was opened. I examine how a captive population can be initiated by removing fish from the wild without unduly accelerating extinction risk for the pupfish in Devils Hole. I construct a count-based PVA model, parameterized from estimates of the intrinsic rate of increase and its variance using counts in spring and fall from 1995-2013, to produce the first risk assessment for the pupfish. Median time to extinction was 26 and 27 years from spring and fall counts, respectively, and the probability of extinction in 20 years was 26-33%. Removing individuals in the fall had less risk to the wild population than harvest in spring. For both spring and fall harvest, risk increased rapidly when levels exceeded six adult pupfish per year for three years. Extinction risk was unaffected by the apportionment of total harvest among years. A demographic model was used to examine how removal of different stage classes affects the dynamics of the wild population based on reproductive value (RV) and elasticity. Removing eggs had the least impact on the pupfish in Devils Hole; RV of an adult was roughly 25 times that of an egg. To evaluate when it might be prudent to remove all pupfish from Devils Hole for captive breeding, I used the count-based model to examine how extinction risk related to pupfish population size. Risk accelerated when initial populations were less than 30 individuals. Results are discussed in relation to the challenges facing pupfish recovery compared to management of other highly endangered species.
    Full-text · Article · Sep 2014 · PeerJ
  • Source
    • "Artificially reared organisms are thus subject to adaptation to captivity (i.e. domestication selection; Frankham et al. 2002; Ford et al. 2008). Large-scale, human-mediated releases of plants and animals occur worldwide, and when artificially reared individuals are released to the wild, there can be negative genetic effects on native or wild populations (reviewed in Laikre et al. 2010). "
    [Show abstract] [Hide abstract]
    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 F(1) 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.
    Full-text · Article · Oct 2012 · Molecular Ecology
  • Source
    • "Anderson et al.[20] observed consistent directional selection on body length, favoring large size in both sexes. In contrast, and similar to our study, Seamons et al.[18] and Ford et al.[19] observed fluctuations in the mode and direction of selection on this trait in both sexes. Such results may reflect temporal variation in intraspecific competition. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Background A number of studies have measured selection in nature to understand how populations adapt to their environment; however, the temporal dynamics of selection are rarely investigated. The aim of this study was to assess the temporal variation in selection by comparing the mode, direction and strength of selection on fitness-related traits between two cohorts of coho salmon (Oncorhynchus kisutch). Specifically, we quantified individual reproductive success and examined selection on date of return and body length in a wild population at Big Beef Creek, Washington (USA). Results Reproductive success and the mode, direction and strength of selection on date of return and body length differed between two cohorts sampled in 2006 and 2007. Adults of the first brood year had greater success over those of the second. In 2006, disruptive selection favored early and late returning individuals in 2-year-old males, and earlier returning 3-year-old males had higher fitness. No evidence of selection on date of return was detected in females. In 2007, selection on date of return was not observed in males of either age class, but stabilizing selection on date of return was observed in females. No selection on body length was detected in males of both age classes in 2006, and large size was associated with higher fitness in females. In 2007, selection favored larger size in 3-year-old males and intermediate size in females. Correlational selection between date of return and body length was observed only in 2-year-old males in 2006. Conclusions We found evidence of selection on body length and date of return to the spawning ground, both of which are important fitness-related traits in salmonid species, but this selection varied over time. Fluctuation in the mode, direction and strength of selection between two cohorts was likely to be due to factors such as changes in precipitation, occurrence of catastrophic events (flooding), the proportion of younger- versus older-maturing males, sex ratio and densities of spawners.
    Full-text · Article · Jul 2012 · BMC Evolutionary Biology
Show more