Optimizing the Connectivity of Salmon Farms: Role of Exposure to Wind, Tides, and Isolation

Industry targets for a global rise in aquaculture demand an increase in output over the next decade. Salmon farm operators seek to meet this need either by the establishment of new locations, or by the expansion of existing sites. Finding space for new sites can be challenging, due to interactions between them and with the surrounding environment. As a result, operators are looking towards more physically exposed areas in which to place sites. Parasitic sea lice pose a particular environmental challenge and public concern. Enhanced availability of host fish at farms can allow lice to reach much greater numbers than they would in the absence of farms. Operationally, threshold abundances are used to define when management action should be taken, but there is no agreed approach to determine whether a particular proposed development will present an unacceptable risk in terms of heightened sea lice infestation levels and consequent risk to wild fish. We demonstrate the use of biophysical models in assessing physical suitability and parasite risk for two hypothetical farm sites. In a broader context, we demonstrate how infestation pressure is likely to decrease with farm isolation, and to a lesser extent with wave exposure