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AEI
Aquaculture Environment Interactions

    AEI prepress abstract   -  DOI: https://doi.org/10.3354/aei00391

    Development of a risk assessment for sea trout in coastal areas exploited for aquaculture

    Bengt Finstad*, Anne D. Sandvik, Ola Ugedal, Knut W. Vollset, Ørjan Karlsen, Jan G. Davidsen, Harald Sægrov, Robert J. Lennox

    *Corresponding author:

    ABSTRACT: Aquaculture production in Norway is regulated based on the potential for salmon lice impacts on wild fish, but most consideration has been given to impacts on wild Atlantic salmon, despite the fact that anadromous brown trout largely spend their marine phase in coastal waters, where salmon lice have the highest impact. In the present study, we first suggest changes in the marine feeding area and marine feeding time as sustainability indicators for first-time migrant sea trout. This was done on the basis that high salmon lice densities may exclude sea trout from otherwise usable habitat and can necessitate that trout return early to freshwater. Further, a biophysical model method was developed to serve as a proxy for this indicator. The method accounted for the size, migration timing and spatial extent of sea trout and was demonstrated in 2 Norwegian salmon aquaculture production areas, Hardangerfjord (PO3) and Romsdalsfjord (PO5). Change in marine feeding area and marine feeding time differed between PO3 and PO5 and within the areas based on a comparison of 2 focal rivers from each. Sea trout migrating to sea late (June 5) were always more affected than those migrating early (April 24) or intermediate (May 15). Spatial and temporal aspects can greatly influence the potential impacts of salmon lice on sea trout populations and our model revealed dramatic potential impacts. Considering the negative impacts of salmon lice on sea trout, it is necessary for a holistic view of the environmental interactions between aquaculture and wild species that depend on habitats exploited for production.