A researcher whose past work has caused heated debate on the Pacific Coast says she has new data showing fish farms are to blame for sea-lice infestations in wild salmon.
Alexandra Morton, who has been criticized for linking farms to a massive collapse of salmon stocks in several rivers, said a spring survey in the Broughton Archipelago indicates wild salmon in the area are facing extinction.
"If this continues, in the end you won't have wild fish," Ms. Morton said. "I truly am watching . . . an extinction."
She said she sampled 5,000 juvenile wild salmon and found they became infested with sea lice as they swam past fish farms. "Before they hit a farm, they look fine. Then they become infested with lice, and within a few kilometres there's no more salmon [left alive] . . . It takes very, very few lice to kill them."
She said the juvenile salmon, which are migrating out of the rivers where they hatched this spring, usually carried between five and 15 sea lice each. A single parasite can kill a small juvenile salmon, but a larger fish can survive until it carries several, she said.
"Within a short time, they wither down to a whip of a body behind their head. . . . They are dead in a few weeks."
In 2001, Ms. Morton predicted a collapse of wild pink salmon stocks in the Broughton area, between northern Vancouver Island and mainland British Columbia, saying fish farms had caused a major sea-lice infestation. Salmon runs in several rivers in the area fell from about four million fish to about 150,000. But critics questioned her conclusions because pink salmon stocks often go through huge population swings.
Last month, Ms. Morton shored up her argument in an article published in the Canadian Journal of Fisheries and Aquatic Sciences that said wild salmon sampled near fish farms were more heavily infected with parasitic sea lice than those farther away. Again, her views were challenged.
Laurie Jensen, president of Positive Aquaculture Awareness, a group that promotes B.C.'s $300-million fish-farming business, said Ms. Morton produced exaggerated and misleading information.
"The activists don't care whether their analysis conforms to basic scientific principles or not," Ms. Jensen said. "Ultimately, their aim is to make the front page of the newspaper and scare the public with misleading headlines."
Scott McKinley, who holds the senior Canada research chair of animal sciences at the University of British Columbia, has dismissed Ms. Morton's past research. "There is no study published showing a cause-and-effect relationship between sea lice on wild and farmed fish. . . . All the work that's out there is based on correlations."
John Pringle, a research scientist with the federal Department of Fisheries and Oceans, said Ms. Morton has raised interesting questions, but has not proved a link. "I think her work shows [that]where you have salmon farms, you have more sea lice," he said. "But sea lice are natural in the environment . . . the question is what is the source?"
Only two sea-lice infestations, in 1962 and in the 1970s, have been documented in wild salmon stocks on the Pacific Coast, and both occurred before salmon farms began to appear in B.C., Mr. Pringle said.
He said Fisheries and Oceans researchers captured 200,000 juvenile wild salmon last year in the Broughton area, and subjected 20,000 to laboratory examination in one of the most intensive studies of its kind. They found 25 per cent of the young wild salmon had sea lice.
He said the sea lice were different from the species Ms. Morton found in her studies, and that the researchers did not find the same level of infestation she has described. Their study, however, was done after fish farms in the Broughton area were closed during the spring migration of juvenile wild salmon. This year, the fish farms were reopened.
The Fisheries and Oceans study was conducted to determine the impact of sea lice on juvenile salmon, not to see if salmon farms were the source of the infestation.
"Ms. Morton's hypothesis is that, yes, there is a link, but that has not been established," Mr. Pringle said.
Rick Routledge, a Simon Fraser University statistics professor who has worked with Ms. Morton, said he thinks her studies are sound.
"I am solidly on her side on this one," he said. "The evidence implicating the fish farms remains circumstantial and incomplete, but it is very compelling."
A backdrop to the scientific debate is a continuing controversy over whether open-net salmon farms, which usually raise imported Atlantic salmon, should be allowed in B.C.