Effective number of breeders in relation to census size as management tools for Atlantic salmon conservation in a context of stocked populations

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Perrier, Charles | April, Julien | Cote, Guillaume | Bernatchez, Louis | Dionne, Melanie

Edité par CCSD ; Springer Verlag -

International audience. Monitoring short-term fluctuations in effective population sizes (Ne) and effective number of breeders (Nb), as well as their ratio to adult census population size (Ne/Nc and Nb/Nc), provide insight into population demography and inform conservation programs towards limiting long-term loss of evolutionary potential in wild populations. In this study, we monitored short-term variations of Nb and Nb/Nc over three consecutive years for nine Atlantic salmon populations from Quebec, Canada. We documented how these population genetic parameters were influenced by anadromous population size as well as yearly and long-term stocking intensity. Towards this end, 15 microsatellites were used to genotype about 100 one-yearold parrs for each of three consecutive years for nine genetically distinct populations (total n = 2506) from Que´bec, Canada. Yearly stocking intensity had a negative effect on Nb/Nc, possibly as a consequence of a reduced reproductive contribution of stocked relative to wild fish. However, the impact of long-term stocking intensity on Nb/ Nc was not significant, which may indicate relatively weak carry-over effects of stocking on future generations. Also, Nb/Nc was negatively correlated with NC, suggesting compensatory mechanisms, as previously reported in other salmonids. Overall, this study provides evidence of relatively weak and short-term effect of stocking on Nb/Nc ratio in Atlantic salmon populations and suggests potential biological mechanisms leading to the significant negative relationship between Nb/Nc and Nc.

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