Quantifying heritable variation in fitness-related traits of wild, farmed and hybrid Atlantic salmon families in a wild river environment

Abstract

Farmed fish are typically genetically different from wild conspecifics. Escapees from fish farms may contribute one-way gene flow from farm to wild gene pools, which can depress population productivity, dilute local adaptations and disrupt coadapted gene complexes. Here, we reanalyse data from two experiments (McGinnity et al., 1997(McGinnity et al., , 2003 where performance of Atlantic salmon (Salmo salar) progeny originating from experimental crosses between farm and wild parents (in three different cohorts) were measured in a natural stream under common garden conditions. Previous published analyses focussed on group-level differences but did not account for pedigree structure, as we do here using modern mixed-effect models. Offspring with one or two farm parents exhibited poorer survival in their first and second year of life compared with those with two wild parents and these group-level inferences were robust to excluding outlier families. Variation in performance among farm, hybrid and wild families was generally similar in magnitude. Farm offspring were generally larger at all life stages examined than wild offspring, but the differences were moderate (5-20%) and similar in magnitude in the wild versus hatchery environments. Quantitative genetic analyses conducted using a Bayesian framework revealed moderate heritability in juvenile fork length and mass and positive genetic correlations (40.85) between these morphological traits. Our study confirms (using more rigorous statistical techniques) previous studies showing that offspring of wild fish invariably have higher fitness and contributes fresh insights into family-level variation in performance of farm, wild and hybrid Atlantic salmon families in the wild. It also adds to a small, but growing, number of studies that estimate key evolutionary parameters in wild salmonid populations. Such information is vital in modelling the impacts of introgression by escaped farm salmon.

Can variation in standard metabolic rate explain context‐dependent performance of farmed Atlantic salmon offspring?

“…For the hybrid families, however, there was no significant effect of egg size on survival.In contrast to several published results showing that hybridization between farmed and wild Atlantic salmon results in offspring that display lower survival in nature than wild offspring(McGinnity et al, 2003;Reed et al, 2015;Skaala et al, 2012), we did not detect significantly lower survival of the hybrid juveniles than that of their wild half-siblings. For the hybrid families, however, there was no significant effect of egg size on survival.In contrast to several published results showing that hybridization between farmed and wild Atlantic salmon results in offspring that display lower survival in nature than wild offspring(McGinnity et al, 2003;Reed et al, 2015;Skaala et al, 2012), we did not detect significantly lower survival of the hybrid juveniles than that of their wild half-siblings.…”

Modeling fitness changes in wild Atlantic salmon populations faced by spawning intrusion of domesticated escapees

“…Based upon results from these simulations, together with existing knowledge, we suggest that a combination of reduced spawning success of domesticated escapees, natural selection purging maladapted phenotypes/genotypes from the wild population, and phenotypic plasticity buffer the rate and magnitude of change in phenotypic and demographic characteristics of wild populations subject to spawning intrusion of domesticated escapees. These suggestions are in line with empirical data demonstrating that domesticated escapees display reduced spawning success in comparison with wild salmon (Fleming et al., , ), the offspring of domesticated salmon display reduced survival in the wild when compared to wild fish (Fleming et al., ; McGinnity et al., , ; Skaala et al., ) and that differences between domesticated and wild salmon in phenotypic traits, such as growth rate, are much less pronounced in the wild than in the hatchery (Besnier et al., ; Jonsson & Jonsson, ; Reed et al., ; Skaala et al., ).…”

Ancestry and adaptive evolution of anadromous, resident, and adfluvial rainbow trout (Oncorhynchus mykiss) in the San Francisco bay area: application of adaptive genomic variation to conservation in a highly impacted landscape

“…Species can respond to environmental change by moving to the most suitable habitat (Harrisson, Pavlova, Telonis‐Scott, & Sunnucks, ), or through rapid changes in their phenotype (Darimont et al., ). Rapid adaptation to novel environmental conditions can in turn lead to directional change in the frequency of variants in specific genomic regions (Houde, Fraser, & Hutchings, ; Lamaze, Garant, & Bernatchez, ; Pearse, Miller, Abadía‐Cardoso, & Garza, ; Reed et al., ). In addition, increased phenotypic plasticity may allow organisms in variable environments to match their phenotype with the optimum trait value (Tufto, ) leading to an increase in mean population fitness (Ezard, Prizak, & Hoyle, ).…”