Stocking represents the most important management tool worldwide to increase and sustain commercial and recreational fisheries in a context of overexploitation. Genetic impacts of this practice have been investigated in many studies, which examined population and individual admixture, but few have investigated determinants of these processes. Here, we addressed these questions from the genotyping at 19 microsatellite loci of 3341 adult lake trout (Salvelinus namaycush) from 72 unstocked and stocked lakes. Results showed an increase in genetic diversity and a twofold decrease in the extent of genetic differentiation among stocked populations when compared to unstocked. Stocked populations were characterized by significant admixture at both population and individual levels. Moreover, levels of admixture in stocked populations were strongly correlated with stocking intensity and a threshold value of total homogenization between source and stocked populations was identified. Our results also suggest that under certain scenarios, the genetic impacts of stocking could be of short duration. Overall, our study emphasizes the important alteration of the genetic integrity of stocked populations and the need to better understand determinants of admixture to optimize stocking strategies and to conserve the genetic integrity of wild populations.

With the decline of many exploited fish populations, catch and release has become an increasingly used management practice to allow sport fishing while reducing its impact on wild populations. However, survival and reproductive success can vary according to the catch and release technique and environmental conditions, suggesting a potential impact of this practice on prespawning behaviour. Here we evaluate how some critical aspects of salmon freshwater migration are influenced by catch and release and by environmental factors. For this purpose, 40 multi-sea-winter Atlantic salmon (Salmo salar) (20 catch and release and 20 control) were followed by telemetry from June 2011 to March 2012. Temperature was found to influence movements and the daily probability that a fish would cross a fish ladder, while water discharge influenced daily distance travelled during the prespawning migration. Catch and release was found to influence the daily probability of fish to cross a barrier as well as the total distance traveled in the river. Overall, this study suggests that salmon caught and released by fishermen survive and reproduce, but that prespawning exploration behaviours could be altered compared with those of uncaught salmon.

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Documenting habitat-related patterns in foraging behaviour at the individual level and over large temporal scales remains challenging for large herbivores. Stable isotope analysis could represent a valuable tool to quantify habitat-related foraging behaviour at the scale of individuals and over large temporal scales in forest dwelling large herbivores living in coastal environments, because the carbon (δ13C) or nitrogen (δ15N) isotopic signatures of forage can differ between open and closed habitats or between terrestrial and littoral forage, respectively. Here, we examined if we could detect isotopic differences between the different assemblages of forage taxa consumed by white-tailed deer that can be found in open, closed, supralittoral, and littoral habitats. We showed that δ13C of assemblages of forage taxa were 3.0‰ lower in closed than in open habitats, while δ15N were 2.0‰ and 7.4‰ higher in supralittoral and littoral habitats, respectively, than in terrestrial habitats. Stable isotope analysis may represent an additional technique for ecologists interested in quantifiying the consumption of terrestrial vs. marine autotrophs. Yet, given the relative isotopic proximity and the overlap between forage from open, closed, and supralittoral habitats, the next step would be to determine the potential to estimate their contribution to herbivore diet.