Sea Lice Threaten Fish Farms

by Wayne Cullen

Pink salmon returns were big eve­rywhere this year except, once again, the Broughton Archipelago, where fish farms are suspected of causing smolt death due to sea lice infections. The Coastal Alliance for AquacultureReform issued a news release in late September stating the rivers of the Broughton remain virtually empty for the second year in a row.

Early reports from Depart­ment of Fisheries and Oceans (DFO) confirm these disappointing results, which had been predicted by research biologist, Alexandra Morton. Morton, a long-time resident in the area, has been studying the salmon situation for several years.

DFO was similarly pessimistic in their 2003 preseason forecast: “The possibility that sea-lice infestations observed around the Broughton Ar­chipelago during the fry migration in 2002 will adversely affect survival cannot be discounted.”

A spokesman from the Salmon Farmers Association, Odd Grydeland, points out that salmon farms have existed in the Broughton for 17 years without significant problems. Since DFO will be releasing research find­ings from a $1 million study of pink salmon later this year, Mr. Grydeland was quoted as saying that it’s prema­ture “to blame fish farms for an out­break of lice in wild stocks.”

In reply, Morton says that her tests in other areas where there were no fish farms, showed considerably less incidence of sea lice than the Broughton. Morton also says the number of farms has increased over the years, and more importantly, the density of the fish has increased from about 250,000 per farm to, in some cases, over one million. The fish farms these days are like “sea-lice condominiums,” says Morton.

Not One Louse

Morton says some species of baby fish can handle a certain, normal degree of lice, but the young pinks heading out to sea are too small (.3 grams) to survive even one louse.

Meanwhile, without waiting for the results of a new DFO study, which should be released this November, the province has allowed farmers to restock some of the fallowed sites in the Broughton.

Next year’s numbers will prob­ably show an improvement because some of farms were fallowed while the smolts were heading out to sea. (Most fallowing was done because of IHN infections that killed off whole crops – 6 farms in 18 months.) But unless the results of the DFO research include a strong cautionary warning, it looks as though there will be no fal­lowing for next spring’s run.


Instead fish farms will simply use “Slice,” a chemical/pharmaceutical that kills sea lice. There are problems with Slice, according to Morton. The chemicals involved kill not only sea lice, which are crustaceans, but other crustaceans such as shrimp and prawns as well, and even organisms on which the pink smolts feed on their way to sea.

Why not move the farms else­where? First, the very water condi­tions — good temperatures and pro­tected areas — which make the region perfectly suited to wild fish, make it ideal for farmed fish. Also the Island highway is nearby, making transport to market convenient.

In a bizarre twist, while the DFO studies were on-going, a separate DFO study has confused the issue. The David Suzuki Foundation sug­gests that the research methods of the parallel study were poor. Morton agrees, saying that they were using trawling to catch the fish, a method which tends to scrape the lice off the fish before they can be inspected.


Credits: p. 12. & p. 14

Rockfish photo from National Oceanic and Atmospheric Administration (NOAA) Photo library

Leaping salmon photo from National Oceanic and Atmospheric Administration (NOAA) Photo library:

[From WS November/December 2003]

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