Saskatchewan

Dead fish in Wascana Lake victims of 'natural population control': ecologist

There has been an unpleasant sight — and smell — on the shores of Wascana Lake over the last few days, but an ecologist says there's no cause for concern.

Majority of fish are common carp, an invasive species

Large numbers of dead fish have turned up on the shores of Wascana Lake over the last few days. (Cory Coleman/CBC)

There has been an unpleasant sight — and smell — on the shores of Wascana Lake over the last few days, but an ecologist says there's no cause for concern.

Large numbers of dead fish have turned up, creating a scene one might expect in a horror movie.

Sarah Romuld, an ecologist with the Provincial Capital Commission (PCC), said it's all part of the life cycle.

"Right now we're kind of experiencing a natural, kind of, response to springtime," Romuld said.

Sarah Romuld, an ecologist with the Provincial Capital Commission, said winter kill provides balance in Wascana Lake by freeing up more resources for other types of fish. (Cory Coleman/CBC)

She said that during long and cold winters, similar to what Regina experienced this year, large amounts of ice can prevent dissolved oxygen from getting into the water. Furthermore, bacteria begins to grow as the ice melts and uses up some of the oxygen already in the water.

"Right now we're seeing the result of the demand far outweighing the supply in terms of oxygen," she said.

Romuld said fish are less active in the winter and don't require as much dissolved oxygen. That changes as the weather heats up because fish start moving around more.

Essentially, the weather warms up and some fish don't get enough oxygen to survive.

Invasive species

Romuld said most of the dead fish are common carp.

"We see a lot of common carp here in the lake during the fish kill because they're the ones that are most sensitive to those changes and to those lower levels of dissolved oxygen in the water," she said.

Fish kill, also known as winter kill, happens every year. Romuld said there are more dead fish in the lake this year because of the harsh winter.

She said there's no reason to be concerned.

"Common carp are invasive and we ideally don't want them here," she said.

"If they're the ones that are most susceptible to the lower levels of dissolved oxygen, great, because it is that natural population control."

Winter kill provides balance

She said winter kill provides balance in Wascana Lake by freeing up more resources for other types of fish.

"We have a very healthy fish population here given that it's a prime area for them. There's no fishing. They have food and they have open space," she said.

The fish population is carefully monitored, according to Romuld. The PCC is able to increase the amount of dissolved oxygen if need be.

Most of the dead fish are common carp, an invasive species. (Cory Coleman/CBC)

She said the decaying fish could alter the chemical components in the water, but it would be minimal as the fish are usually eaten by birds and other animals. Flowing water also helps wash away the remains.

She said the amount of time for the dead fish to decay, or be cleaned up, is dependant on weather. The PCC is asking the public to stay away from the fish.

If anyone finds a dead fish outside of the water they are asked to contact the PCC.

ABOUT THE AUTHOR

Cory Coleman has worked at CBC Saskatchewan as a producer, associate producer and reporter. Have a story idea? Email cory.coleman@cbc.ca

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