Abstract
Abstract Salmon lice infestation is a major challenge for the aquaculture industry in Norway, threatening wild salmonid populations and causing welfare problems for farmed salmon. Lice dispersion and infestation patterns are simulated by combining a high-resolution hydrodynamic model for the Norwegian coast and fjords with an individual-based model for salmon lice. We here present results from Altafjorden, a sub-arctic fjord with large stocks of wild salmonids, where the inner part is protected as a National Salmon Fjord. The outer part of the fjord hosts several fish farms, and our simulations demonstrate how ocean currents can disperse lice between farms as well as into the protected part of the fjord. The relative contributions from the farms in the different parts of the fjord depends on their locations relative to the currents and circulation patterns in the fjord. Knowledge of how the highly variable water currents disperse salmon lice within fjord systems is necessary for managing farm locations and production quotas, if the goal is to minimize infestation pressure on wild salmonids and between fish farms.
Highlights
The salmon louse (Lepeophtheirus salmonis) is a parasite naturally present in the Norwegian coastal waters, but in areas with intensive salmon farming the elevated number of available hosts has increased the amounts of lice far beyond natural levels (Costello, 2009b; Serra-Llinares et al, 2014; Taranger et al, 2015; Thorstad et al, 2015; Serra-Llinares et al, 2016)
We have presented results from the first high-resolution modelling study of salmon lice growth and dispersal in a fjord under typical summer conditions in Finnmark, the northernmost part of Norway
The Regional Ocean Modelling System (ROMS) hydrodynamic circulation model has been evaluated in several studies from Norwegian waters by comparing with hydrographic and current measurements, both in regional, openocean applications (Lien et al, 2013a, b, 2014; Skarðhamar et al, 2015; Hattermann et al, 2016; Lien et al, 2016) and coastal applications (Myksvoll et al, 2012; Asplin et al, 2014; Johnsen et al, 2014)
Summary
The salmon louse (Lepeophtheirus salmonis) is a parasite naturally present in the Norwegian coastal waters, but in areas with intensive salmon farming the elevated number of available hosts has increased the amounts of lice far beyond natural levels (Costello, 2009b; Serra-Llinares et al, 2014; Taranger et al, 2015; Thorstad et al, 2015; Serra-Llinares et al, 2016). Aquaculture activity is projected to continue to grow substantially in the future (Anon., 2014–2015) Most of this growth will occur in Northern Norway where there is still available space, as well as favourable growth conditions for farmed salmon. This can create serious conflicts of interest, as Northern Norway is a very important region for wild Atlantic salmon populations (Anon., 2016; www.nasco.int/convention.html).
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