Yukon's Eagle mine failure comes during 'disastrous' salmon run

Cyanide solution leaking at Eagle Mine near Mayo, Yukon, may have complex impacts on the surrounding environment — but especially, experts say, on salmon. 

On July 4, Yukon government officials said cyanide concentration levels of 0.04 milligrams per litre were detected in nearby Haggart Creek, which is on the traditional territory of Na-Cho Nyäk Dun. 

Few details have been shared about the amount of cyanide present in the groundwater in the area from the territorial government, but several experts on the ground told CBC they believe there is significant leaching of cyanide solution into groundwater at the site.

That news comes as first reports roll in on the summer's returning salmon numbers. The Stewart River watershed is an important thoroughfare for spawning salmon and connected to Haggart Creek. 

"We're seeing historically disastrous run levels right now," said Dennis Zimmermann, a board member for the Yukon salmon sub-committee.

Researchers say groundwater contamination is likely to have longer, more serious consequences as cyanide doesn't dilute or degrade as quickly underground as it does on the surface. 

Elliott Skierszkan, an assistant professor in earth science at Carleton University, works to understand the movement of contaminants in water. 

"Once present in groundwater, cyanide can persist for several years in a slow-moving contaminated plume," Skierszkan told CBC over email. "If uncontrolled, a plume can be a long-term source of cyanide transfer back to surface water environments."

Salmon 'acutely vulnerable' to cyanide

Som Niyogi, a professor at the University of Saskatchewan, studies the effects of contaminants on aquatic organisms and has monitored the impacts of industrial metals at northern sites like Yellowknife's Giant Mine. 

While more cyanide is expected to enter the creek in the coming weeks, Niyogi said the initial numbers reported from the government were already worrying.

"That could be acutely toxic to some of the salmonids like rainbow trout, chinook salmon and arctic grayling," he said.

Niyogi said levels as low as 0.01 milligrams per litre can still have "significant chronic effects" if fish are continually exposed over 20 or 30 days.

He cited a series of studies which found exposures of 0.01 milligrams per litre reduces the overall physiological performance of fish by around 50 per cent.

"Cyanide has a wide range of toxic effects in fish. It can affect their ability to breathe, but it also can cause reproductive and developmental effects," he said.

This could mean diminished egg production and embryos with a lower chance of survival. 

Not only are fish more sensitive to cyanide than many other species, Niyogi says, but salmonid fish in particular are far more sensitive than other fish. 

He said the situation has members of the Yukon Salmon Sub-Committee "deeply concerned" given preliminary data on returning salmon. 

"We're at such a desperate time with respect to this chinook run right now that every salmon counts," said Zimmermann. "Every egg in the gravel, every little fry, every out migrating smolt, every returning adult is so important right now."

Zimmermann said "the timing is horrible" with respect to spawning adult salmon as well as returning juvenile salmon. 

"Those little fry and migrating smolts are incredibly important and they're very susceptible to water quality," he said. "They need free-flowing, cold, crisp, clear water. And that's something that we've always been very proud of and something that we've advocated for at the tables internationally with Alaska."

Earlier this year, parties on both sides of the border agreed to a historic seven-year moratorium on fishing chinook. 

"This is definitely something that concerns us and is … beyond a blemish to our reputation internationally as we negotiate salmon treaties."

Experts say eating fish that have been exposed to cyanide is unlikely to be risky. But heavy metals like arsenic, present in Eagle mine ore and wastewater, bioaccumulate. This means concentration of these substances can be higher in animals than in the environment.

Matt Lindsay is a professor at the University of Saskatchewan specializing in mine closure and groundwater geochemistry.

"It doesn't mean necessarily that people couldn't go on the land, but it might change how they interact with the land," said Lindsay. "Many of those metals end up having chronic effects and causing things like cancer and, you know, failures of body functions."

Lindsay has previously toured the Keno City area, around 20 km from Eagle Mine, with Na-Cho Nyäk Dun members. 

"I feel for all Yukoners, but particularly the people of Mayo and Na-Cho Nyäk Dun," he said. "It's very clear they have a lot of pressure on their land and resources and from the mining sector. And this is… it's devastating for them."

The First Nation has said that the severity of contamination from cyanide and other chemicals has not been publicly conveyed, and that the spill will have implications for all life in the region.