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Dryad

Data from: The effects of hybridization and parasite infection on predation survival and behaviour of endangered landlocked salmon – implications for genetic rescue

Data files

Jan 20, 2025 version files 1.89 MB

Abstract

A prerequisite of genetic rescue in endangered and genetically depauperate populations is to pre-evaluate between possible pros and cons of hybridization for the life history and survival of the target population. We hybridized critically endangered Saimaa landlocked salmon (Salmo salar m. sebago) with one of its geographically closest relatives, anadromous Baltic salmon. In two experiments conducted in semi-natural streams during overwintering (at age 1.5 years) and in early summer (age 2+), we studied how hybridization and infection of eye parasites (Diplostomum pseudospathaceum) affected fish survival under predation from Northern pike (Esox lucius). Additionally, we recorded movements of the juvenile salmon to explore the effect of hybridization and infection on antipredatory behaviour (movement activity and habitat use). Among the uninfected groups, mortality of hybrid salmon was significantly lower (14.5%) compared to purebred landlocked salmon (37.2%), supporting a positive effect of hybridization under predation risk. This benefit, however, was removed by the parasite infection, which impaired vision and increased the susceptibility of fish to predation. The negative effects of infection were particularly pronounced in the anadromous salmon due to its lower infection resistance compared to the landlocked salmon. Hybridization per se did not affect activity levels of salmon, but overwintering activity correlated positively with eye cataract coverage, and summer activity was highest in anadromous salmon. These results demonstrate that controlled hybridization of a small animal population with a genetically more diverse population could entail both positive and negative implications, at least in the first crossbred generation.