Salmon louse infestation levels on sea trout can be predicted from a hydrodynamic lice dispersal model ...

• Main Authors: Bøhn, Thomas, Nilsen, Rune, Gjelland, Karl Øystein, Biuw, Martin, Sandvik, Anne, Primicerio, Raul, Karlsen, Ørjan, Serra-Llinares, Rosa, Sandvik, Anne Dagrun, Serra‐Llinares, Rosa Maria
• Format: Dataset
• Language: English
• Published: Dryad 2021
• Subjects: sea trout; aquaculture and wild fish interactions; management; parasite-induced health effects; Salmon Lice; surveillance data; hydrodynamic model; FOS: Agriculture, forestry, and fisheries; Atlantic salmon
• Online Access: https://dx.doi.org/10.5061/dryad.9ghx3ffjj; https://datadryad.org/stash/dataset/doi:10.5061/dryad.9ghx3ffjj

The abundance of the parasitic salmon louse has increased with the growth in aquaculture of salmonids in open net pens. This represents a threat to wild salmonid populations as well as a key limiting factor for salmon farming. The Norwegian ‘traffic light’ management system for salmon farming aims to increase aquaculture production while securing sustainable wild salmonid populations. However, this system is at present solely focusing on mortality in wild Atlantic salmon, while responses of sea trout with different ecological characteristics are not included. We analyze lice counts on sea trout from surveillance data and use Bayesian statistical models to relate the observed lice infestations to the environmental lice infestation pressure, salinity, and current speed. These models can be used in risk assessment to predict when and where lice numbers surpass threshold levels for expected serious health effects in wild sea trout. We find that in production areas with the highest density of salmon farms (West ... : More than 1100 locations are approved for aquaculture production along the Norwegian coast, but 600-700 are simultaneously active in production. These locations are distributed in 13 management/production areas (hereafter production areas) (Fig. 1). The production areas were defined to minimize cross-dispersion (Ådlandsvik 2015). We analysed a data set of n=2937 sea trout < 200 g, sampled at 40 different sites in 2019 (the most recent data at the onset of this work) (Fig. 1). The fish were caught in traps and gillnets (17 – 21 mm mesh size) in week numbers 20-31 (mid-May to end of July) with a gradual delay from south to north (Table 1). The sampling thus targeted post-smolts recently migrated out from the rivers, a migration that is delayed from south to north by about 6 – 8 weeks (Kristoffersen et al. 2018; Johnsen et al. 2020). Table 1. Week, production area and the number of sea trout we counted lice on. Production area Week 1 2 3 4 5 6 7 8 9 10 11 12 13 20 32 0 0 0 0 0 0 0 0 0 0 0 0 21 31 165 162 73 ...