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A juvenile pink salmon infested with sea lice.
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Sea lice
The impacts of sea lice on wild salmon in B.C. have been devastating, in some cases resulting in a 97 percent decline of wild stocks.Sea lice are small parasites that occur naturally on many different species of wild fish. Sea lice feed on marine fish by attaching to the outside, usually on the skin, fins or gills.
Sea lice eat the mucous, blood and skin of salmon. While a few lice on a large salmon may not cause serious damage, large numbers of lice on an adult fish, or just one louse on a juvenile salmon, can be harmful or fatal. The feeding activity of sea lice can cause serious fin damage, skin erosion, constant bleeding, and deep open wounds.
Salmon farms are typically located in sheltered bays and inlets near rivers on or near the migratory routes juvenile salmon use to reach the ocean. The adult fish in salmon farms create an unnatural reservoir of sea lice that are particularly deadly for juvenile wild pink and chum salmon heading for the ocean. Before commercial-scale salmon farming began, sea lice numbers were typically low in the spring because the number of available hosts in coastal areas was also low.The juveniles are at risk because of their small size and the stresses associated with changes that occur when they enter saltwater. Just one or two sea lice are enough to kill a juvenile pink salmon newly arrived in saltwater. Much higher numbers have been observed recently on juvenile pink salmon near B.C.’s salmon farms.
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"Wherever there are fish farms there are lice. Wherever there are no fish farms there are no lice. It's very simple science." Alexandra Morton www.callingfromthecoast.com |
Science is clear
A substantial and growing body of research published in peer-reviewed journals indicates that sea lice are dangerous to wild salmon. Cutting edge research published in the journal Science in December, 2007 was the first study to calculate the impact individual wild salmon mortalities have on the population of a whole run.Sea lice infestations of wild juvenile pink salmon all associated with salmon farms have depressed wild pink salmon populations and placed them on a trajectory toward rapid local extinction in B.C.’s Broughton Archipelago.
The Science study shows louse-induced death of pink salmon is commonly over 80 percent and exceeds previous fishing mortality.
The study concludes:
- If outbreaks continue local extinction is certain, and a 99 percent collapse in pink salmon population abundance is expected within two salmon generations (four years) of the study’s publication date
- A 99 percent population collapse means that in just four short years, the pink runs will disappear impacting the bears, orcas, eagles, seals, sea lions and trout that they sustain
- The decaying bodies of pink salmon also fertilize riparian forests and maintain the nutrient levels for aquatic plants, insects, amphibians, and fish in rivers. The loss of pink salmon populations will erode the entire coastal ecosystem, threatening the survival of not only the flora and fauna but the communities and economies that depend on these resources.
Sea Lice and Salmon by Watershed Watch Salmon Society
Disease
Open net cage salmon farms are essentially floating feedlots. The large number of fish in a small space provide the perfect conditions for diseases to breed and spread throughout the farm and to wild salmon.
Although diseases carried by farmed and wild salmon are often caused by the same viruses and are naturally occurring, the density of fish within a farm can cause disease to rapidly spread throughout the farm, much in the same way that infectious diseases spread quickly among children in schools.
Industry representatives and government officials often insist that diseases cannot spread from farmed to wild salmon. Salmon farmers are in denial when they claim that diseases can spread from wild to farmed fish, but not the other way around.
