After the dramatic collapse of sockeye salmon stocks in the Fraser River last year, the Department of Fisheries and Oceans quickly identified the three "most likely" causes - including a mysterious disease that causes brain lesions in fish.
Details of the disease, which scientists are still trying to understand, are outlined in internal DFO documents obtained by The Globe and Mail under an Access to Information request filed by researcher Ken Rubin.
"The evidence of brain lesions is new and it will take some time to document the geographic extent and to understand a relationship (if any) between a disease agent and mortality," states a Dec. 11, 2009, Memorandum for the Minister signed by deputy Minister Claire Dansereau.
The document identifies "three high profile and/or likely causes" of the sockeye collapse, but focuses on the disease, promising to describe the other top suspects - sea lice from fish farms and a lack of food in the Pacific - in future briefings.
The cause of the Fraser's sockeye collapse, when only about one million salmon returned instead of the more than ten million that were expected, is the focus of a judicial inquiry appointed by Prime Minister Stephen Harper.
Ms. Dansereau and Paul Sprout, then DFO's regional director general for the Pacific region, were both on the witness stand at the Commission of Inquiry into the Decline of Sockeye Salmon in the Fraser River on Tuesday, but were not questioned about the disease, which may be raised when the commission turns to scientific matters.
In an Oct. 8, 2009, email to Ms. Dansereau, Mr. Sprout, who is now retired, listed 10 possible causes of the sockeye collapse. But in her subsequent memo, Ms. Dansereau narrowed the list to three, and focused on one - a disease associated with a pattern in the way some genes become active in salmon as they make their way back to freshwater.
Ms. Dansereau said the brain lesions were first detected in 2009, in samples collected from 2006.
"In subsequent examinations . . . [DF0]staff found lesions in the brains of southern BC coho, chinook, and sockeye salmon, and across a range of life stages and sample years. . . . The gene response pattern and the presence of lesions have not been directly linked, but they are thought to be related to a viral infection. Molecular screening to date has not yielded a positive identification. Parasitic infections are also likely present," the memo states. "Analysis is ongoing. However, given its widespread distribution, the disease agent is thought to be endemic."
Ms. Dansereau said sockeye "experienced 30-60 per cent higher mortality while approaching the coast and in the river than salmon that did not show the gene response pattern."
The note says the gene response pattern is thought to be related to a virus from the retroviral family, but "few retroviruses have been described in salmon and no conclusive identification of a specific retrovirus has been made."
Ms. Dansereau said studies were under way into the new disease and "other high profile potential causes: sea lice and low food abundance."
Mr. Sprout declined to comment when approached at the inquiry, and Brian Wallace, the commission's senior counsel, interrupted to say witnesses under oath cannot answer media questions.
At the inquiry, Tim Leadem, a lawyer representing a coalition of environmental groups, asked DFO officials how they dealt with the "conflicting mandates" of promoting fish farm development and protecting wild salmon habitat.
"I acknowledge there is a potential [conflict]" said Ms. Dansereau. "We need to find the right balance to ensure the [aquaculture]industry and the wild fishery survive. It's not an easy road to walk down."
Ms. Dansereau and other senior DFO managers are expected to be recalled for further testimony at the inquiry, headed by B.C. Supreme Court Justice Bruce Cohen. The inquiry is scheduled to run through next spring.Report Typo/Error