King Township is aware of reports of dead fish in stormwater management ponds across the GTA, including here in King. Experts believe the most likely cause is winterkill – a natural phenomenon where fish die due to a lack of oxygen in the water during long winters. The frequency and impact of winterkill is largely determined by the severity of the winter and the resulting ice cover that develops.
Naturally occurring bacteria consume leaves and other organic matter, depleting the oxygen available for fish, resulting in a die-off. The fish become visible as the ice cover melts. Another contributing factor is that stormwater management ponds are not designed to serve as fish habitats but rather as functional infrastructure intended for managing rainwater and snowmelt.
King Township reminds residents not to release wild or domestic fish into stormwater ponds, to avoid touching or handling dead fish, and to keep pets and children away from affected areas.
