Lake Huron's 'fish city' is a sign of trouble at nuclear plant, says Ontario First Nation
Story by CBC/Radio-Canada
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The dazzling underwater footage from Lake Huron appears to show such abundance that a documentary crew dubbed a zone "fish city" and showcased it for Earth Day.
But Saugeen Ojibway Nation (SON) is challenging that narrative of fish crowding in the warm-water outflow of Bruce Nuclear Generating Station — saying the site functions instead as a "fish trap."
The First Nation points to the deaths of up to five million gizzard shad there in 2025 — a tally recorded by the Department of Fisheries and Oceans (DFO) in a Canadian Nuclear Safety Commission regulatory report.
The mass die-off occurred when enough fish entered the station to clog cooling water intake systems and force a proactive shutdown of Bruce A Unit 2 by the utility.
SON also says several lake sturgeon — a species at risk, considered culturally important in Anishnaabe teachings — became stranded in a forebay pond at the plant. One was rescued in November by Bruce Power and SON, while three remain.
The clash over "fish city" is about more than imagery. It raises questions about how Bruce Power manages ecological risk as it seeks permission from regulators to increase plant limits in order to run reactors at a higher output to produce more electricity.
(Submitted by Saugeen Ojibway Nation)
SON says warm water is 'bait'
Bruce station is North America's largest nuclear plant and releases water as part of its reactor cooling system that is warmer than the surrounding lake. While it's clear fish gather there, regulators didn't cite the plant as the cause of the die-off.
However, Ryan Lauzon, a biologist with SON and an adjunct professor at the University of Toronto who authored a 136-page study on the 2025 fish kill paid for by the First Nation, said the site operates in two stages: attraction and entrapment.
A lake sturgeon, a species at risk and culturally revered by many Indigenous nations, including Saugeen Ojibway Nation, is seen in June 2024 in a forebay pond at Bruce Nuclear Generating Station. (Submitted by Saugeen Ojibway Nation)
"You have this thermal effluent, which is the bait," he said.
Lured by the warm waters and higher food availability within, Lauzon said the fish can, depending on conditions, be pulled into the plant's forebay — a channel inside the plant's water intake system that feeds cooling water to station equipment — once there, larger fish often have no way out.
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"There's no real access for them to exit the plant," he said. "Just the fact there's all these fish swimming around outside the nuclear plant doesn't necessarily mean health."
"These fish are actually at risk."
Bruce Power disputes claim
Bruce Power disputed claims the plant caused the 2025 die-off, saying unusual environmental conditions, such as high shad numbers and harsh winter conditions, played a a major role.
"This combination led to a broad, population-level die off observed across the region," the utility said in an email.
(Bruce Power)
Bruce Power said it also added nets, acoustic and strobe-light deterrents as well as sonar and camera monitoring and expanded its lake research to keep fish out of its system, following the 2025 die-off incident.
The Canadian Nuclear Safety Commission said staff visited the plant three times in March and February of 2025 to confirm the measures had been put in place and said it would continue to monitor their effectiveness.
Seeking increased power limits
In August 2025, Bruce Power asked regulators for permission to generate more electricity from its existing reactors, saying the plant could increase output by about 11 per cent by 2030, from roughly 6,300 to 7,000 megawatts, without building a new reactor.
A final hearing on the matter is scheduled for July 2026.
Maggie Tieman, the director of community and external affairs at Bruce Power wrote in an email to CBC News that the requested increase is needed to help meet rising provincial electricity demand and can be made safely, while staying within environmental limits.
"Due to improvements in pump flow, the reactor power increase requested will not increase temperature differences outside of regulated limits," she wrote. "No operational changes can be implemented without regulator assessment and approval."
No benchmark for fish deaths
At the same time, the company acknowledged in a 2024 report, the year before the mass die-off and reactor shutdown, regulators had no clear benchmarks for judging how many fish deaths are unacceptable when fish are pinned to intake screens or drawn into plant systems.
Bigmouth buffalo swim among other species in a dense 'fish city' near the Bruce nuclear plant, part of a shifting mix of fish in Lake Huron. (Inspired Planet)
"No benchmarks for fish impingement or entrainment are available from federal or provincial authorities that can be used to assess the environmental risk. Effect thresholds are dependent on sufficient knowledge of the population including natural variability," the report said.
It means that while Bruce Power does operate under strict regulatory rules, there is no clear threshold for when fish losses become unacceptable.
Shad play role in lake health
Paul Jones, a retired fisherman who spent roughly two decades working Lake Huron and is now a councillor with the Chippewas of the Nawash Unceded First Nation, part of Saugeen Ojibway Nation, said that while many people dismiss gizzard shad as junk fish, the mass die-off removed an important food source from the lake ecosystem that affected other species.
"You take out all that kind of nourishment out of the lake, it's going to have some sort of effect," he said, noting many people in his community view fish as a gift.
Gizzard shad are extremely sensitive to water temperature and will often seek out warm water effluents as a refuge against winter. These shad, seen in the Thames River in London, Ont., in 2021 gathered in the warmth from storm sewer runoff. (Colin Butler/CBC News)
"We always say that fish give up its life so that we could utilize it, so that we could sustain ourselves."
Jones said the fish deaths matter both ecologically and culturally: shad provide food in the lake, while fish are treated with respect in Ansihnaabe teachings. It underscores why he believes celebratory "fish city" portrayals "missed the mark."
"If you do that, you don't really have to fix anything."
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