Salmon louse infestation levels on sea trout can be predicted from a hydrodynamic lice dispersal model
Permanent lenke
https://hdl.handle.net/10037/23746Dato
2021-12-13Type
Journal articleTidsskriftartikkel
Peer reviewed
Forfatter
Bøhn, Thomas; Nilsen, Rune; Gjelland, Karl Øystein; Biuw, Martin; Primicerio, Raul; Karlsen, Ørjan; Serra Llinares, Rosa MariaSammendrag
2. We analyse lice counts on sea trout from surveillance data and use Bayesian statistical models to relate 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.
3. We find that in production areas with the highest density of salmon farms (West coast), more than 50% of the sea trout experienced lice infestations above the levels of expected serious health effects.
4. We also observed high lice infestations on sea trout in areas with salinities below louse tolerance levels, indicating that fish had been infested elsewhere but were returning to low-saline waters to delouse. This behavioural response may over time disrupt anadromy in sea trout.
5. The observed infestations on sea trout can be explained by the hydrodynamic lice dispersal model, which provides continuous estimates of lice exposure along the whole Norwegian coast. These estimates, which are used in Atlantic salmon research and management, can also be used for sea trout.
6. Synthesis and applications. Wild sea trout, spending its entire feeding migration in fjords and coastal areas, is at higher risk than wild Atlantic salmon to lice infestations from industrial salmon farming. The high levels of lice infestation we observed on sea trout question the environmental sustainability of the current aquaculture industry in areas with intensive farming. We discuss the complex responses of sea trout to salmon lice and how the Norwegian ‘traffic light’ management system may include data on sea trout.