Washington researchers present findings of Clayoquot sea lice study

JENNIFER DART, special to Westerly News 21 January 2010 Link to article

A group of Washington researchers have found sea lice on juvenile wild salmon samples in Clayoquot Sound and the levels they found were higher in close proximity to salmon farms.

The Wild Fish Conservancy -- a non-profit organization dedicated to preserving, protecting and restoring wild fish and the ecosystems they depend on through science, education and advocacy -- sent a team of three researchers to Clayoquot early last year to begin to identify potential causes for the "collapse" of wild salmon stocks in the area.

"Something in Clayoquot Sound is very broken," lead research Audrey Thompson told a crowd gathered at the Clayoquot Field Station Jan. 14.

As a place where not a lot of research has been done, she said the WFC saw this area as "a good place to fill a data gap."

The team came to answer the question of whether there are sea lice infestations on wild salmon in Clayoquot Sound, and also whether there is a correlation between the presence of infestations and the location of aquaculture farms.

The answer to both questions was yes, Thompson told the crowd during the presentation.

But Thompson stressed their data represents only one year in a complex life cycle in a complex environment. "This is just one piece of the puzzle," Thompson said. "We have to find pieces and put them together before we can make progress."

Clayoquot Sound is an ideal place to study the issue of declining stocks, she said, because of the pristine habitat of its river systems.

"Freshwater habitat is often blamed for salmon declines, but in Clayoquot Sound, freshwater habitat is abundant yet salmon runs are small, and shrinking," Thompson told the Westerly. "Salmon farms are the first non-pristine thing Clayoquot fish encounter, so studying their potential impacts first seemed like a logical place to start."

Many other potential factors can influence the health of juvenile salmon, she noted, including ocean temperatures, predators and food abundance.

Sea lice are also a naturally occurring parasite, but other scientists (notably in relation to aquaculture in the Broughton Archipelago) have linked the presence of salmon farms to the juvenile salmon infestation, Thompson said. Juvenile salmon, which are still developing, are most vulnerable to sea lice, she said.

In Clayoquot, the team collected 5,000 samples of juvenile chum and Chinook salmon over a five-month period from February to June.

They collected the fry in a large net that was towed behind their boat, put them in plastic bags for 30 seconds in order to count the lice on them. The fry were then returned to the water.

The team also looked at water temperatures and salinity levels at different depths in each of the areas they studied. The research will be peer reviewed and published, Thompson confirmed, and samples will be kept for future review.

By way of an example, Thompson detailed the team's findings in the Bedwell River system. She said in March they found few lice, and the numbers gradually increased as the season went on until in May roughly 80 per cent of the juvenile salmon leaving the Bedwell system had at least one louse attached to them.

The rate of infestation in the Bedwell was higher than in other systems, she said. (Mainstream Canada, Clayoquot Sound's largest salmon aquaculture company, has five farm sites in Bedwell Sound).

For the purposes of the study, Thompson said they considered a "lethal load" of lice to be 1.6 lice per one gram of fish. There was discussion among audience members during the question period about this number.

Laurie Jensen, Environmental, Compliance and Community Relations Manager for Mainstream Canada, asked why the team used the 1.6 figure when Fisheries and Oceans Canada consider three lice per one gram of fish to be a lethal load.

Thompson said the number is based on other research.

Josie Osborne said she considered this point to be the most important one: "What's a lethal load on juvenile salmon? Maybe it's 1.6, maybe it's three," said Osborne, noting there is uncertainty in the scientific community. "But for us, the public, and for them, the decision makers, the question is what are the numbers we're going to use to decide whether certain things are harmful or not harmful?"

WFC executive director Kurt Beardslee said the lethal load question can be misleading, because even a small amount of sea lice can cause a fish to act differently and be more vulnerable to predators.

Fish farms are required to report when they are using chemicals like the one used to treat sea lice, noted one audience member.

Another wondered if farms aren't experiencing blooms, where do the lice come from?

"If they don't come from farms then that's another big question mark," responded Thompson. "I don't know where they come from."

It would be useful to have information from salmon farms, such as fish counts, age, lice counts, etc., said Kevin Bruce, the Friends of Clayoquot Sound's office coordinator.

"It would be very helpful and I hope that in the future it will be shared," agreed Beardlee.

When asked if the team approached the farm for that information, Beardslee said, "I didn't think it was appropriate to ask, they were asking us to leave."

Thompson said the team is finalizing plans to return to the area to continue their study.

"If any place has a high likelihood of being able to return to a healthy environment, you guys are sitting on incredible potential..." Beardslee said.

"It's why we wanted to come here -- the pay back is faster here than anywhere else."

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