Sea lice are a naturally occurring phenomenon whereby the parasites infect wild migrating salmon, usually without serious harm because the lice fall off when the salmon enter fresh water. Open net-pen salmon farms pack wildly unnatural numbers of farmed Atlantic salmon in coastal locations which results in wildly unnatural blooms of parasitic sea lice that transfer between wild and farmed fish. Since the farmed salmon are trapped and do not enter fresh water, the lice are able to cause extensive serious harm to the adult caged fish.

In 2020, Dalhousie University’s Dr. Jeff Hutchings was approved for a second year of funding from ASCF totaling $40,350, to continue researching temperature-dependent effects of sea lice on Atlantic Salmon.

In Norway, Scotland, Ireland, and Pacific Canada, huge numbers of sea lice from salmon farms have been implicated in declines of wild populations due to high infestation and resulting mortality levels in wild juvenile salmon as they migrate in close proximity to the cages.
Sea lice affect the growth, survival, physiology, and behaviour of wild salmon, and it’s possible that these effects will worsen as our coastal waters continue to warm from climate change. To investigate the temperature-dependent effects of sea lice on Atlantic salmon, a laboratory experiment was conducted in which juvenile Atlantic salmon were infected with sea lice across a range of temperatures. Survival was tracked and body growth and organ development of the fish were measured throughout the experiment. Blood, skin, and kidney samples were also collected to assess the stress and immune responses of the hosts.

Using these results, this project will evaluate how temperature and sea-louse infestation affect stress and immune responses, growth, mortality, and organ development of Atlantic salmon. The results of this project will be shared with scientists, DFO managers, and the public.