Nine-year study confirms sea lice outbreaks on farms cause wild salmon declines—better farm management a short-term solution
Vancouver—Treating farm salmon with pesticides to control sea lice, well before wild juvenile pink salmon migrate past farms, has reduced lice outbreaks on wild fish and allowed their populations to begin recovering in the Broughton Archipelago, British Columbia. A study published in the journal Ecological Applications by Canadian scientists, including researchers from Watershed Watch Salmon Society and the University of Alberta, examined changes to the management of sea lice on farm salmon and the subsequent response of wild salmon populations. Environmental non-government organizations concerned with the risks associated with farm-derived sea lice pressured industry about the issue and became involved in this research.
The timing of the administration of the pesticide known as Slice®—which is widely used by the industry and milled into pellets and fed to farm fish—is a critical factor in reducing sea lice numbers on wild salmon. The researchers found that when pesticides are fed to farm fish in late winter—before wild juvenile pink salmon begin their migration—outbreaks on the migrating wild fish were lower than in previous years with later treatments.
Current regulations in B.C. stipulate that if the average number of mature sea lice exceeds 3 per farm fish during the months March to June, the salmon farm must administer Slice® or harvest the fish. This policy was implemented in 2003 to help protect wild juvenile pink salmon during their outmigration period. However, that timing window may be too late, according to this new study. “Government regulators should take note of this independent research and consider adjusting sea lice management regulations accordingly,” said Stephanie Peacock, University of Alberta.
Sea lice have developed resistance to pesticides in many areas including eastern Canada and Norway; it may only be a matter of time before it becomes ineffective in B.C. Another risk associated with Slice is that it can pass freely into the marine environment through the open-nets of farms and may negatively affect crab, shrimp, prawns, and other animals. “Although our study highlights a potential beneficial farm management strategy for sea lice; at best it’s only a band-aid solution due to the risks and limitations associated with pesticides like Slice®,” said Dr. Craig Orr, Watershed Watch Salmon Society.
The study is timely given the recent $26 million Sockeye Inquiry Final Report which also concludes that salmon farming is a risk to wild fish. “Our study adds to an increasing weight of evidence detailing the threats open-net salmon aquaculture poses to wild fish,” said Stan Proboszcz, Watershed Watch Salmon Society. “In light of our study and the recent Sockeye Inquiry Final Report, government should act immediately to eliminate the risks associated with salmon farming.”
Contact the authors of the study for more information:
Stephanie Peacock, Researcher, University of Alberta (780) 492-1636
Craig Orr, Executive Director, Watershed Watch Salmon Society (604) 809-2799
Stan Proboszcz, Fisheries Biologist, Watershed Watch Salmon Society (604) 314-2713
Abstract available online: http://www.esajournals.org/doi/abs/10.1890/12-0519.1