Sea Lice Infest More Fish Stocks

Further Infestations Found in Discovery Islands Salmon Populations

Apr 1, 2008

Reports of sea lice infestations to young salmon have been limited to the Broughton Archipelago, BC. Researchers have now found them on fish near the Discovery Islands.

A recent research paper reports that sea lice infestations near fish farms are spreading to the Discovery Islands region of British Columbia and affecting multiple species of fish. Alexandra Morton, Rick Routledge, and Martin Krkosek prepared this study entitled Sea lice infestation of wild juvenile salmon and herring associated with fish farms off the east central coast of Vancouver Island, BC that was published in the North American Journal of Fisheries Management.

A previous study by Morton and Routledge, Mortality Rates for Juvenile Pink and Chim Salmon Infested with Sea Lice in the Broughton Archipelago, identified harmful infestations of sea lice in young Pink salmon migrating past fish farms on the Broughton Archipelago. This paper was published by the Alaska Fishery Research Bulletin for the Alaska Department of Fish and Game.

Sea Lice and Salmon Farming - Sea lice (Lepeophtherirus salmonis and Caligus clemensi) are naturally occurring parasites of salmon. Research conducted in several countries shows the link between salmon fish farms and infestations of sea lice in nearby wild juvenile salmon. Transmission of sea lice from farmed fish to young wild salmon migrating near farm rearing pens is usually fatal to juvenile fish. While an adult salmon can easily tolerate the presence of many sea lice, two or three of the parasites prove deadly to smaller immature salmon. Researchers worry that salmon farms located near the mouths of spawning rivers could cause the collapse of wild salmon populations.

Infestations Found in the Discovery Islands, BC Region - Up until the release of this study, the only region of British Columbia to see a problem with sea lice infestation of salmon was in the Broughton Archipelago region of British Columbia. Researchers have now identified the same problem for wild fish stocks in BC's Discovery Islands region. Economically significant runs of fish migrate through this area to spawning areas on the Fraser River, Campbell River, eastern Vancouver Island, and inlets on the lower mainland.

Affected Fish Stocks - While sea lice only affected Pink salmon in the Broughton Archipelago region, numerous species are being impacted in the Discovery Islands near fish farms. Among these are wild stocks of juvenile Pink salmon, Chum salmon, Sockeye salmon, and herring. Sea lice infestations are uncommon for young fish that live away from fish farms. Recreational and commercial fishing of wild salmon in the Discovery Islands and Campbell River region brings hundreds of millions in dollars to the Provincial economy.

A Connection to Salmon Farms - Researchers studied the many factors sea lice depend on for maintaining an abundant population. These included water temperature, salinity of the water, timing of sample selection, host species, and exposure to salmon fish farms. Exposure of wild fish to nearby fish farms was the only consistent and significant predictor of sea lice abundance. Wild fish exposed to sea lice flourishing in fish farms were infected with more sea lice than those living outside the periphery of the installations.

The report concludes, "These results underscore an urgent need to develop and implement conservation policy that protects wild salmon."

The copyright of the article Sea Lice Infest More Fish Stocks in Marine Habitats is owned by Alan Sorum. Permission to republish Sea Lice Infest More Fish Stocks in print or online must be granted by the author in writing.