A Yukon Energy maintenance project at Whitehorse dam led to 761 fish deaths last fall, prompting new protocols to protect river ecosystems.
Dam Work Leaves Hundreds of Fish Dead
At least 761 fish were killed below the Whitehorse dam during maintenance last fall, according to a consultant’s report obtained through an access to information request. The findings, prepared by Environmental Dynamics for Yukon Energy, confirm water levels dropped too quickly during scheduled work in October 2024, stranding fish in sensitive areas.
The Event Behind the Loss
Crews had been removing fish screens and supporting steel beams from the facility’s turbines—a seasonal task required before the Yukon River freezes. To perform the work safely, water levels were drawn down by about a metre in some areas. This rapid reduction, the report states, “led to a rapid dewatering of sensitive areas” where fish became trapped.
Impact on Species
The mortality included 447 slimy sculpin—an important cold-water indicator species—172 juvenile Arctic grayling, 133 longnose suckers, and a single juvenile chinook salmon. The number of fish deaths exceeded levels recorded in previous years, raising concern among fisheries officials and environmental groups.
Conditions That Made It Worse
Unusually high water levels in the Yukon River combined with limited storage capacity in Schwatka Lake forced Yukon Energy to lower flows more quickly than planned. That acceleration amplified the risk, making it harder for fish to adapt to shifting conditions. The Department of Fisheries and Oceans confirmed it is investigating but declined further comment.
Company Responds to Findings
Yukon Energy says it is taking steps to prevent a repeat of last year’s incident. Technical working group member Kirsten Hogan explained that the company is revising its water “ramping” protocols, aiming to lower flows more gradually to mimic natural seasonal changes. This, she said, gives fish a chance to move out of danger zones before stranding occurs.
Preventing Future Stranding
Beyond adjusting flow rates, the utility has mapped areas most prone to fish stranding and plans closer monitoring. Mechanizing the removal of fish screens, such as using lifts, is also under consideration. “We know the importance of these fish to First Nations and to the Yukon River ecosystem,” Hogan said. “Our focus now is to make sure this doesn’t happen again.”
Stay connected with Canada’s latest headlines — follow Maple News Wire on Instagram | Facebook | X | LinkedIn.
