Friends of Clayoquot Sound: Fish farming: The Killing of Sea Mammals

Chemical treatments: Slice® the lice

Recent science has shown that the health of some B.C. wild salmon stocks has been threatened by the spread of sea lice—a parasitic crustacean that commonly flourishes in the cramped conditions of open net-cage salmon farms.

Sea lice occur naturally on many different species of wild fish. However, the unusual and unnatural conditions created by salmon farms are ideal for sea lice outbreaks. Millions of farmed salmon crowded in an open net-cage salmon farm suspended in the ocean allow sea lice to proliferate and spread to wild juvenile salmon nursery areas with devastating effects.

Salmon farmers (just like other farmers who grow crops and livestock) often treat their product with pesticides in order to control pests.. In Canada, the preferred treatment for sea lice outbreaks on open net-cage salmon farms is the pesticide called Slice®.

Slice® contains the chemical emamectin benzoate, a poison that affects the nerve cells of crustaceans. Slice is added to farmed salmon feed. The medicated feed is eaten by farmed fish, absorbed through the gut and subsequently circulated throughout the tissues. Sea lice that are feeding on a farmed salmon’s skin, fins and/or gills ingest the toxin and die.

In Clayoquot Sound, Mainstream uses Slice® on their salmon farms to combat sea lice. Here are some facts about Slice® (emamectin benzoate) use in B.C.’s and Canada’s salmon farms:

Until 2009, Slice® was available to fish farmers for limited use through Health Canada’s Emergency Drug Release program, which allows the use of unapproved drugs when recommended by veterinarians for emergeny situations.
In June 2009, Health Canada quietly approved the use of Slice®. Research was conducted by the manufacturer, is proprietary, and is not available to the public.
Warning labels on plant pesticides that contain emamectin benzoate (e.g., Proclaim™) recommend that the product not be applied directly to water, areas where surface water is present, or to intertidal areas below the mean high tide mark. Nevertheless, Slice® is applied to salmon feed and dumped directly into the ocean.
The US Food and Drug Administration has listed emamectin benzoate as an unapproved drug that should not be used on fish destined for consumption in the U.S. According to Canadian government data, on average, this chemical is being used at least once during the production of every farmed salmon from BC – and over 80% of B.C.’s farmed salmon goes to the U.S. market.
Data on the quantity of Slice® used are not publicly reported but are available through the BC Ministry of Environment. However, these data are inaccurate and unverified by the farm companies.
Slice® is so toxic that it takes only a few grams of the chemical to treat tonnes of salmon feed.
Until 2009, Health Canada recommended a minimum delay of 68 days between administering Slice® and harvesting, to allow the chemical in treated fish tissue to decline to an acceptable level. Since Slice was approved by Health Canada in 2009, this delay is no longer required.
It is not known if repeated applications of Slice® can be made without harmful effects to non-target organisms as diverse as crabs, prawns and zooplankton.
The potential for cumulative environmental loading and negative effects based on repeated use has not been formally assessed in Canada or any other country.
There are no data on Slice® or its metabolites in waters surrounding Canadian fish farms after application.
The effects of Slice® on larval crustaceans (zooplankton) has not been examined in detail and there is no information on the effect this toxin has on microbes.
The effects of wide spread coordinated geographic use of Slice® on non-target organisms is completely unknown. The pesticide is commonly applied to a number of salmon farms at the same time in the same geographic area.
It’s not a question of if, but rather when sea lice will develop resistance to Slice®. Reports from Chile, Norway and Canada’s east coast have indicated that sea lice are already showing signs of resistance. What then? Other even more toxic chemicals?

Treating fish with chemicals and dumping toxins into the ocean is no way to farm fish. Many of the problems associated with open net-pen salmon farming, including sea lice, would be eliminated with closed containment fish farms. It’s time for government and industry to move towards implementing closed containment technology.

PO Box 489, 331 Neill St., Tofino BC V0R 2Z0
250-725-4218 info@focs.ca