MILJØ2015-Norsk miljøforskning mot 2015

The overall aim of the project is to advance the understanding of evolutionary and demographic effects of escaped farmed Atlantic salmon on wild salmon populations using and extending existing mathematical models. Artificial selection for increased gro wth performance in farmed salmon have led to changes also in other morphological and behavioural traits and a reduction in relative fitness of farmed fish in the wild. To understand how natural selection is balanced by continual immigration of farmed fis h into wild populations, the effects of selection and migration in several traits simultaneously will be modelled. Previous models for selection-migration balance suggest that wild salmon populations can reach alternative stable evolutionary states depen ding on the history of intrusion of farmed fish. The project aims at highlighting how the evolutionary trajectory towards such alternative equilibria depends on current management actions. Unknown quantities in the model will be estimated from tests of genetic change in populations experiencing contrasting levels of intrusion of farmed fish and from existing published data. Using stochastic models with finite population size the effects of local inbreeding and random gene frequency fluctuations on popu lation fitness can be assessed. Such models can also encompass more realistic assumptions about the underlying genetic basis of the traits under selection and can thus be used to check the validity of more idealized quantitative genetic models. Finally, the project will investigate at what rate genetic variation in the system of farmed and wild salmon as a whole is lost. Previous work suggest that pure one-way migration of farmed fish into the wild makes this stongly dependent on the number of individu als in the breeding lines and how the breeding lines are structured into into either four parallels or one merged population. This will examined by further developing exisiting population genetic models.