Notice: May 5, 2025 - Fish Die-Off Event - Humber Bay Area and Etobicoke Waterfront
- We’ve been receiving a number of reports recently. TRCA staff have investigated and identified the fish as alewives. This species typically spawns at this time of year, moving from deep water to the warmer nearshore areas. However, they are highly sensitive to rapid temperature changes. When strong winds or storms cause cold water upwellings, the sudden temperature shift can disorient or even kill the fish. We recently experienced such a storm that stirred up the lake while these fish were nearshore for spawning, and what we’re seeing now is the result of that event.
- This is not unusual this time of year and it can fluctuate depending on year and the severity of weather, but we always see it in varying degrees.
For information on how to manage deads animal or fish found on private property, including how to report a fish die-off, please visit Dead animals or fish on your property page on the Government of Ontario website. This page provides detailed guidance on what steps to take and how to report concerns.
Additional information related to environmental monitoring and wildlife health can be found on the Fish and Wildlife Health pages.
