April 24, 2014 6:36 pm

Winterkill: How Ontario’s dead fish are feeding lake ecosystems

Watch video above: Dead fish in Ontario lakes. It’s not as bad as it may look. Laura Zilke reports. 

TORONTO – Hundreds of fish in Ontario lakes were killed over the winter because of the unusually cold weather.

But it’s not a bad thing, say some experts.

At least 100 large-mouth bass, along with pumpkin seed sun fish and rock bass were found dead at Orangeville’s Island Lake, according to Credit valley Conservation authority’s Phil Bird.

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The fish kill is a normal part of winter – this one worse, because the weather was more harsh.

Winter kill is the result of a lack of oxygen for the fish, Rick Portiss, environmental monitoring manager with the Toronto and Region Conservation authority said.

“Whatever oxygen is left in the water gets used up by whatever fish happen to be in the water,” he said.

When the oxygen drops, Portiss said, fish are forced to compete with plants. Plants on the bottom of the lake will begin to die due to a lack of sunlight and when they decay, Portiss said, they use up some of the available oxygen.

There would be more regular thaws during a normal winter allowing oxygen to get into the lake, Bird said. At the Orangeville lake, the ice thickened over the winter reaching a depth of nearly two feet. It finally thawed in mid-April.

But conservationists aren’t worried, in fact it can be a good thing for the lake’s ecosystem.

The fish that wash ashore are recycled back into the ecosystem.  Predators hungry from the harsh winter are feasting on the fish, Portiss said.

“Usually within a couple of weeks after the ice has melted any dead fish that may have been laying around the ponds usually gets cleaned up rather quickly,” he said.

Conservation authorities regularly monitor fish supplies and say the loss isn’t likely enough to harm the ecosystem.

© Shaw Media, 2014

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