Fish kill likely caused by heat wave

Yip explained the phenomenon, known as a summer kill, does not happen every time temperatures rise, but heat can make some bodies of water particularly susceptible.

Fish floating on Tobin Lake

“Unfortunately, its a natural phenomenon that happens during these periods of really hot weather that we got,” he said.

Some fish species are more vulnerable to low oxygen levels than others. Yip said cisco and whitefish tend to be particularly sensitive, although the province has also received reports of dead walleye and northern pike.

Fish that are able to move more easily may be able to seek out areas with higher oxygen levels, Yip said. Oxygen levels can vary in different parts and depths of a lake.

Summer kills have been reported at Tobin Lake and the North Saskatchewan River upstream and downstream of the reservoirs, as well as at Lake of the Prairies, some of the Qu’Appelle lakes, Turtle Lake and other locations.

The phenomenon can also occur in rivers, Yip said. Although moving water can generally benefit from turbulence that introduces oxygen, the North Saskatchewan River is relatively calm and slow-moving in some areas.

Yip said fish kills can be unsightly, particularly when large numbers of dead fish float to the surface, but they typically do not wipe out an entire fish population.

“There’s going to be definitely some localized death of fish and they tend to be quite obvious when they’re dead like that because they float to the top,” he said. “But you’ll still have tons of fish in those rivers and lakes.”

Yip said the fish kills are not expected to have significant long-term effects on fisheries in most cases. The province will, however, consider the impact of fish kills when setting fishing limits each year.

The province also has guidance for anglers on how to reduce stress on fish being released, particularly walleye. Yip said anglers should avoid bringing walleye up from deep water, as rapid changes in pressure can cause barotrauma and increase the risk of mortality.

Despite the fish kills, Yip said recreational anglers and fishing tournaments are not expected to have significant long-term impacts as long as people follow existing fishing regulations and recommendations.

The province is also asking the public to report fish kills they observe in lakes and rivers.

“We do appreciate the reports from the public,” Yip said. “If there are other lakes and other locations that have documented fish kills, we definitely take them seriously and we love getting those reports.”

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susan.mcneil@pattisonmedia.com

by Susan McNeil

Fish kill likely caused by heat wave

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