Beyond hybridization: the genetic impacts of nonreproductive ecological interactions of salmon aquaculture on wild populations

Abstract

Cultured Atlantic salmon Salmo salar are of international socioeconomic value, and the process of domestication has resulted in significant behavioural, morphological, and allelic differences from wild populations. Substantial evidence indicates that direct genetic interactions or interbreeding between wild and escaped farmed Atlantic salmon occurs, genetically altering wild salmon and reducing population viability. However, genetic interactions may also occur through ecological mechanisms (e.g. disease, parasites, predation, competition), both in conjunction with and in the absence of interbreeding. Here we examine existing evidence for ecological and non-reproductive genetic interactions between domestic Atlantic salmon and wild populations and the potential use of genetic and genomic tools to resolve these impacts. Our review identified examples of genetic changes resulting from ecological processes, predominately through pathogen or parasite transmission. In addition, many examples were identified where aquaculture activities have either altered the selective landscape experienced by wild populations or resulted in reductions in population abundance, both of which are consistent with the widespread occurrence of indirect genetic changes. We further identify opportunities for genetic or genomic methods to quantify these impacts, though careful experimental design and pre-impact comparisons are often needed to accurately attribute genetic change to aquaculture activities. Our review indicates that ecological and non-reproductive genetic interactions are important, and further study is urgently needed to support an integrated understanding of aquaculture-ecosystem interactions, their implications for ecosystem stability, and the development of potential mitigation and management strategies.

Genome editing on finfish: Current status and implications for sustainability

“…A sterile fish will not only aid this issue, but it would also be considered a prerequisite for using genome edited fish in ocean pen production. Here, we do, however, want to emphasize the need for more research on how such a sterile salmon would impact wild relatives and surrounding biodiversity when it escapes 119 . Disease resistance could aid any aquaculture sector globally, and it would aid both the economic efficiency of the production, but also animal welfare and the impact on wild stocks, thus both biodiversity and responsible productions aspects of sustainability.…”

“…Here, we do, however, want to emphasize the need for more research on how such a sterile salmon would impact wild relatives and surrounding biodiversity when it escapes. 119 Disease resistance could aid any aquaculture sector globally, and it would aid both the economic efficiency of the production, but also animal welfare and the impact on wild stocks, thus both biodiversity and responsible productions aspects of sustainability. Increased welfare is, alongside with sustainability, assumed an important argument for application of genome editing in aquaculture, especially in a country like Norway where ethical responsibility is implemented in the Act.…”

Farm‐scale models in fish aquaculture – An overview of methods and applications

“…attraction of non-farmed species to farms) caused by the presence of farmed fish, farm structures and waste emission, 161 (v) risks related to the introduction of non-indigenous species 162 and (vi) genetic pollution. 163 Among them, only some environmental impacts related to the release nutrients, pathogens or contaminants can be modelled at the farm level (i.e. using FSMs alone), because other impacts occur due to or rely on environmental drivers related to larger bay-scale and ecosystem-scale processes.…”

“…antibiotics, therapeutants, chemicals) on ecosystems and (iv) changes in food webs (e.g. attraction of non‐farmed species to farms) caused by the presence of farmed fish, farm structures and waste emission, 161 (v) risks related to the introduction of non‐indigenous species 162 and (vi) genetic pollution 163 . Among them, only some environmental impacts related to the release nutrients, pathogens or contaminants can be modelled at the farm level (i.e.…”

Distinct early life stage gene expression effects of hybridization among European and North American farmed and wild Atlantic salmon populations

“…Direct genetic effects can arise through introgression, which increases gene flow by genetic mixing (Glover et al, 2017). On the other hand, indirect genetic effects can occur through nonreproductive ecological interactions (e.g., competition, disease transmission, predation) with farmed conspecifics, which can lead to decreased survival, reduction in population size, and increased genetic drift (Bradbury et al, 2020). A pressing question is to what extent interbreeding between farmed and wild individuals will change the genetics of wild populations.…”