Research Document 1998/158

Genetic introgression of the domestic Atlantic salmon genome into wild populations: a simulation of requirements for conservation

By G. Lacroix, J. Korman, and D. Heath

Abstract

A model was developed to explore the effects that escaped, farmed Atlantic salmon interacting and mating with wild Atlantic salmon could have on the genome and viability of a known wild population. The proportion of escapees spawning, degree of assortative mating, and degree of adaptive differentiation could be varied. After interbreeding occurred, offspring that survived rapidly replaced the pure wild genome or lineage in the population. The survival of these backcrosses was a function of mean genetic introgression of the domestic genome from farmed fish into the population. Model predictions were sensitive to variability in the probability of mating between escapees and other groups, the relative survival of offspring having received some farmed genome, and the number of mature escapees entering a river. In some situations, applying a "hard" natural selection (low relative survival) to offspring with farmed genome (as for distant or differentiated strains) was found to be more beneficial to population persistence than a "soft" selection (as for closely related stocks). The impact of escapees was minimised by early action to eliminate them or prevent them from interbreeding with the wild population. The model identified a need to dramatically decrease response time for applying conservation measures to preserve a low degree of genetic introgression and prevent extinction of the population after escapees were stopped from entering a river, especially at the high proportions of escapees presently found in some rivers. Failure to stop the escape of farmed salmon and their interbreeding with wild salmon resulted in a high mean genetic introgression in backcrosses and eventual extinction of the self-sustaining population. The reported escape of juvenile salmon from commercial hatcheries and their return as spawners of farmed lineage was predicted to greatly accelerate the increase in genetic introgression and to complicate the successful application of conservation measures to preserve the wild population.

Complete document (PDF, 2,402 KB)

Accessibility Notice

This document is available in PDF format. If the document is not accessible to you, please contact the Secretariat to obtain another appropriate format, such as regular print, large print, Braille or audio version.