Decade of sea lice study charted in new report

The report, Assessing the interactions and effects of sea lice on wild salmon populations: final report of project FW0050, sums up the results of a decade of studies and data gathering.

The Marine Directorate says: “In areas of salmon farming activity, levels of planktonic sea lice can become elevated, with farms becoming the primary source of lice in the coastal environment.”

It adds that increased infection of wild fish, based on samples of the wild sea trout population, can be correlated with sea lice numbers on farms.

The report also notes, however, that there has been a decline in adult female sea lice numbers per fish on farms over time since 2015

The report details various wild salmon tracking projects as well as studies on sea lice numbers and treatments, and development of oceanographic models.

It concludes that the project “…has led to standardisation of principles of sea lice modelling, curation of an international dataset for model testing and progress on methodologies for model validation. An increased understanding of sea lice dispersal in the marine environment has been developed and oceanographic modelling has been greatly improved for the Scottish west coast and northern isles. Associated long-term monitoring has quantified an effect of sea lice in the environment on growth rates of sea trout.”

It goes on to say: “There is now increased understanding of the epidemiology of sea lice in Scotland and their impacts on salmon. Through tracking studies, our knowledge of salmon migration and coastal behaviour has increased and, coupled with increasingly sophisticated dispersal models, will inform the further development of a sustainable Scottish aquaculture industry.

“Outputs of this project have made a significant contribution to develop Scotland’s policy and regulatory framework to consider and manage the risk that sea lice from fish farms negatively impact upon wild populations, leading to the development of, and contributing to, delivery of SEPA’s new sea lice risk assessment regulatory framework, with further development on future monitoring and research needs underway.”