Yukon First Nation demands fish passage at Mayo dam and support for salmon restoration

The failure of the Eagle mine in the Yukon last year has created an "existential threat" to one of the First Nation of Na-Cho Nyӓk Dun's most important grayling fisheries, reinforcing the need to protect and restore fish elsewhere — like those in the Mayo River, the First Nation says.

Na-Cho Nyӓk Dun has voiced its concerns in a letter to the Yukon Environmental and Socio-economic Assessment Board (YESAB), as the board undertakes a review of Yukon Energy's application to relicense its Mayo generating station for five years.

Built in the 1950s, the facility in central Yukon consists of a dam and a control structure that have since then obstructed the upriver migration of fish, including chinook salmon, whose numbers have long been in a state of decline. The fish aren't found above the facility anymore.

Na-Cho Nyӓk Dun has been advocating for clear plans and timelines that would allow for salmon to once again access historic spawning grounds.

According to the First Nation, the Mayo hydro facility has affected the ecological health of the Mayo River for decades, with chinook salmon unable to access the upper reaches of the river or Mayo Lake for more than 70 years now. That's upended cultural traditions, altered aquatic and terrestrial ecosystems, and may have caused other collateral damage as the lack of salmon means placer miners can set up operations easier, the First Nation says.

Since the Eagle mine failure, citizens have been fearful of harvesting, including grayling caught along part of the South McQuesten River, a popular spot for citizens in the springtime. Concerns over water quality, the letter states, may force people to go somewhere else to fish, like the Mayo River. But the grayling in that waterway are already vulnerable, the letter states.

"One of the most effective ways to address cumulative effects in the Mayo watershed would be to re-introduce chinook salmon to the Upper Tedze Nyӓk (Mayo River) and create effective fish passage solutions at the two dams," it states, referring to the two structures that make up the Mayo facility.

"This would have the combined effects of connecting isolated fish populations, increasing available habitats for fish, restoring marine derived-nutrients to the system, and reducing the ongoing effects of placer mining."

Michael Muller, vice president of planning, environment, health and safety at Yukon Energy, told CBC News the company is committed to getting things right and working with the First Nation until that happens. 

"We recognize that that facility has stopped salmon from moving upstream," he said. 

What is the First Nation calling for?

The First Nation doesn't want to see the Mayo facility decommissioned. Rather, it wants upstream fish passage and downstream routes made safer. 

There's never been upstream fish passage at either the facility's control structure, which allows for water storage in Mayo Lake so that electricity can be generated during the wintertime, or its Wareham dam.

However, some things could soon change.

Yukon Energy is proposing to replace the control structure. As part of the process, the corporation would also install a fishway that would allow fish like chinook swimming upriver to pass through the dam. The First Nation wants fish passage completed in five years.

However, Yukon Energy hasn't proposed any plans yet for upstream fish passage at the Wareham dam, the larger of the two structures. 

Yukon Energy has previously told CBC News installing upstream fish passage at the Wareham dam could prove very costly.

In its submission to YESAB, Na-Cho Nyӓk Dun acknowledges that.

"However, this does not constitute a valid excuse for inaction or for the [YESAB] Designated Office to fail to specify the necessary mitigation, especially when weighed against the considerable threats facing Yukon River chinook," it states.

The First Nation wants a detailed fish passage plan for the Wareham dam, funds procured, and construction started within five years.

Muller, of Yukon Energy, said plans to secure funding from the federal government are underway. 

"Collaborative processes are important in the long-term."

The dam's spillway at the facility was recently damaged, and its repair is part of a separate process. Still, Yukon Energy has pledged to make the spillway safer for fish passing downstream. 

Na-Cho Nyӓk Dun argues that to conduct a comprehensive assessment, the entire facility needs to be considered, otherwise it's piecemeal. 

"The death of fish through entrainment at the Wareham dam is a significant adverse effect that must be mitigated," it states. "However, specific mitigations are not proposed, nor are the effects well understood."

Entrainment refers to fish being sucked into one dam intake or another because of the flow of water.

According to research commissioned by Yukon Energy, the mortality rate of juvenile chinook salmon killed by decompression and stress at the Mayo facility is roughly 34 per cent. Studies of the lethality of the turbines weren't able to be completed because of limitations with sensors designed to replicate the experience of a fish swimming through the facility.

Na-Cho Nyӓk Dun states turbine mortality could be upward of 20 per cent, a figure that's based on analysis of other facilities, including some in the Columbia River, in B.C. and Washington state.

The First Nation also wants to see salmon restored above the Mayo facility. The headwaters of Mayo Lake include vast wetland complexes, some of which remain intact. 

In February, a fisheries biologist who often works with Na-Cho Nyӓk Dun told Yukon River panel members that areas like these should be unlocked for the species because significant spawning and rearing habitat still exist. 

Na-Cho Nyӓk Dun is already working on this, having partnered with Yukon First Nation Salmon Stewardship Alliance and applied to a Yukon River Panel fund to start laying the groundwork for an upper Mayo River chinook restoration project. 

The First Nation is calling on YESAB to recommend the territory, Ottawa and Yukon Energy help it develop and deliver a salmon rebuilding program in the area.