The high densities of Atlantic salmon in BC salmon farms promote the spread of pathogens and parasites like sea lice. Tavish Campbell photo

Sea lice counts under-reported on B.C. salmon farms: study

Industry association rejects findings over “opaque” methodology

B.C. salmon farms have under-reported sea lice counts in a six-year period, allowing operators to delay or avoid costly delousing treatments during outbreaks, according to a new study.

Using publicly available data from 91 farms between 2011 and 2016, the Simon Fraser University study was published Sept. 7 in the scientific journal Ecological Applications.

It found counts are routinely higher than normal during prearranged audits by Fisheries and Oceans Canada (DFO) officials, suggesting chronic under-reporting when that critical oversight isn’t in place.

“This means that most of the self-reported counts from industry are actually 15 per cent and 50 per cent less than the true numbers of the two species of lice,” said lead author, Sean Godwin, who conducted the research for his PhD at SFU.

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During DFO visits, the study showed mean monthly counts of the Caligus clemensi species rose by a factor of 1.95 per fish, and Lepeophtheirus salmonis by a factor of 1.8.

Fisheries and Oceans Canada (DFO) requires salmon farms to regularly report sea lice counts as part of broad planning to help mitigate the spread to wild juvenile stocks.

A threshold of three parasites per fish will trigger expensive delousing measures, or, as a last resort, a forced harvest before the fish reach optimal size.

Sea lice are naturally occurring in B.C. waters, but farms serve as highly-effective breeding grounds due to the density of salmon hosts available.

The parasites are rarely lethal to adults, but can pose a number of risks to wild juvenile salmon leading to death.

The BC Salmon Farmers Association (BCSFA) rejected the findings of the study and questioned its methodology, saying the authors have constructed an “opaque and complex” model out of relatively simple data.

“It’s not accurate,” Shawn Hall, a spokesperson for the BCSFA said. “The study is presented as a direct comparison of sea lice data from B.C. salmon farms, but it doesn’t actually do that. What they’re reporting on is the variance of historical sea lice counts and what their model said they should have been. It’s faulty. The model is based on assumptions that aren’t clear in the report.

“Our responsibility is to keep the levels of sea lice on farms low, so they don’t transfer back to wild fish. We’re committed to doing that work.”

Godwin defended the model as necessary to account for other factors that affect counts, saying he considered a range of explanations but the model ultimately revealed the same trend as the raw data.

He also agreed with Hall that the results still place counts below the threshold, but added the implications of biased reporting means counts close to that limit would have delayed delousing treatments, if they occurred at all.

Accounting for the study’s findings on under reporting, the number times counts exceeded the three-louse threshold rose from 376 to 437.

Godwin’s research comes three weeks ahead of a Sept. 30 deadline recommendation of the Cohen Commission to remove open-pen farms from a critical salmon migration route in the Discovery Islands if minimal risks are exceeded. The $37-million inquiry into 2009’s decimated sockeye runs also called for policy change at DFO over it’s conflicting mandates of both protecting wild salmon while promoting the salmon farm industry.

The study stated Cohen’s recommendations to collect pathogen data from salmon farms did not consider inaccurate reporting, prompting the authors to offer several policy alternatives to increase the reliability of sea lice counts, including a shift to independent third-party monitoring, or unscheduled audits after counts were made.

“Assuming sea lice aren’t attracted to the fish farms by the presence of DFO employees, these results strongly suggest that counts by industry staff are much less accurate when someone’s not looking over their shoulders,” Dr. Larry Dill, SFU professor emeritus and fellow of The Royal Society of Canada said in a news release.

“The risk to wild salmon is therefore greater than the aquaculture industry would have the public believe, emphasizing the need for greater oversight and regulation.”

DFO were not able to provide a comment in time for publication of this article.

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quinn.bender@blackpress.ca

Salmon farming

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