Nearly two years following an unusual fish incident at Canada’s largest nuclear facility, newly acquired documents reveal the exceptional nature of the event, raising concerns among experts about the increasing challenges posed by unusual ecological circumstances to nuclear plants globally.
In February 2025, an overwhelming number of gizzard shad disrupted the cooling systems at the Bruce Nuclear Generating Station in Tiverton, Ont., resulting in the shutdown of one reactor, decreased power at another, and a significant number of dead fish washing ashore along Lake Huron for an extended period.
Examination of more than 1,200 pages of federal and provincial records by CBC News exposes how an environmental anomaly involving a small, cold-sensitive fish tested the capabilities of Canada’s largest nuclear power facility in unexpected ways.
Bruce Power, the private operator of the plant, declined a televised interview but later issued a written statement without directly addressing specific inquiries from CBC News.
The plant’s internal investigation determined that it faced “a novel environmental event,” with an unprecedented influx of gizzard shad overwhelming the plant’s defenses designed to prevent fish from entering the cooling water system.
The Canadian nuclear regulator described the incident as involving an “uncharacterized and unanticipated volume of gizzard shad,” leading to challenges in maintaining reactor safety at the facility.
Following the disruption caused by the fish event, Bruce Power faced operational challenges, prompting the shutdown of reactors as designed to ensure safety protocols were upheld.
The scale of the fish incident was significant, with millions of gizzard shad congregating near the facility in February 2025, straining the plant’s operations and resulting in a large number of fish casualties.
Experts have noted a rising trend of environmental disruptions affecting nuclear plants globally, with similar incidents reported in other countries, including Romania and France, further emphasizing the need for enhanced adaptation strategies in the face of changing ecological conditions.
In response to the event, Bruce Power has invested approximately $10 million in mitigation efforts and research to prevent future disruptions caused by mass fish gatherings, implementing new technologies and physical barriers to safeguard the plant’s cooling systems.
As nuclear power facilities increasingly play a role in providing low-carbon electricity, the focus on preventing disruptions caused by environmental factors is crucial to ensuring the continued safe and efficient operation of these plants worldwide.
