Trout in Williston Lake are set to go under the knife this summer in the first major study of mercury contamination in the W.A.C. Bennett dam reservoir since the 1980s.
For decades, anglers and First Nations have been warned about eating bull and lake trout from Williston Lake—the world’s seventh-largest reservoir one of just three lakes in the province with a mercury advisory.
However, that advisory is based on 1980s data that many say needs updating.
A two-year study, set to begin this summer, “will provide more information to First Nations and anglers who sometimes worry ‘well, what’s in that fish?’” said Dan Bouillon, regional manager of BC Hydro's Fish and Wildlife Compensation Program.
The outcome of the study will be of keen interest to First Nations impacted by the Site C dam, which will create an 83-kilometre long reservoir in the Peace River Valley.
The Fish and Wildlife Compensation Program (FWCP) is a BC Hydro-funded research agency governed by an independent board, which includes local First Nations, members of the public and provincial and BC Hydro representatives. BC Hydro launched the program in 1988 to study and help minimize the impacts of large hydroelectric projects on aquatic and land-based animals.
In 2012, First Nations members highlighted mercury contamination in Williston Reservoir as their number one research priority, Bouillon said.
Narrower studies have indicated mercury levels in the reservoir are still high, despite being nearly 50 years old.
Last May, West Moberly Chief Roland Willson travelled to the B.C. Legislature with 57 frozen bull trout, which a band study found to be 98 per cent contaminated with mercury. Willson did not immeditately respond to a request for comment May 27.
Early next month, the FWCP plans to release the results of a “snapshot” study conducted last summer, which looked at mercury in a sample of 79 fish.
Bouillon said dam reservoirs tend to have higher levels of mercury contamination when they’re first flooded. However, there’s still “dynamic” change taking place in Williston Lake's fish populations.
“That reservoir is almost 50 years old, and you’d think it must be all settled, everything’s normal, the mercury’s gone down,” Bouillon told a meeting of the Peace River Regional District May 26. “In fact, when it comes to fish in that reservoir, there’s still dynamic change happening.”
He said in the last decade, Williston Reservoir has seen large increases in kokanee, which are prey for larger species like trout, as well as a decline in the number of whitefish. As predators, trout tend to have higher concentrations of mercury.
“Theoretically in Williston Reservoir, we’ve come down to that baseline level (of mercury), but we don’t have all the data to take a close look at that,” Bouillon said.
The program will also distribute kits to nearby First Nations to help them store fish samples for testing.
The joint review panel appointed to scrutinize Site C concluded in May 2014 that not enough is known about how mercury will impact fish in that dam’s reservoir.
A third Peace River dam “would have modest effects on health, which could be mitigated, although the health effects of methylmercury on people who eat the reservoir fish require more analysis to be sure,” the panel wrote.
Site C was approved in late 2014. Construction on the $8.8 billion project began in July.
The W.A.C. Bennett dam was completed in 1968 and produces around 20 per cent of B.C.’s electricity.
The FWCP is also conducting a five-year study on moose mortality in the Williston Lake area, which included tagging 58 animals with sattelite tracking collars. According to a 1975 study, moose populations in the Peace Region fell from 12,500 to 4,000 after the completion of the dam due to habitat loss and drowning.
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