Bow fishing restrictions stressed by weather, other rivers take effect Saturday

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Provincial officials hope to take advantage of the threats facing fish in the Bow and other southern Alberta rivers by imposing fishing restrictions that begin Saturday.

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From 2:00 p.m. to 12:00 p.m. every day, rod fishing will be prohibited in the Bow and other rivers in the south and southwest of the province to give a break to fish stressed by the low water level that caused high temperatures.

The fishing restrictions, which affect the Bow River East Slopes Fishery Management Zone 1 and the St. Mary River below St. Mary Reservoir, are expected to last until August 31.

That will encompass the Bow River from Banff to Bassano, “and all of northern Calgary to the Montana border, the Oldman and Bow River watersheds,” said Paul Christensen, senior fisheries biologist with Alberta Environment and Parks.

The decision was made after recent hot weather brought the temperature of the Bow River to 20C for five consecutive days. The threshold necessary to make such a decision is reached when the water temperature exceeds 20 C for three or more consecutive days, and when the flows at the bow are below the 25th percentile of water flow for four or more days.

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“The lower level of the water causes the temperature to warm up even faster and makes the fish more vulnerable,” Christensen said.

Warmer water contains less oxygen for fish, which are further stressed by angling, “so we’re trying to stop that activity during the very hot part of the day,” he added.

It’s an action taken unexpectedly, he said, after last winter’s heavy snowpack and a subsequent melt.

But he said the current persistent heat wave has caused river flows to decline with little water from the mountains replacing them, a trend likely to continue for years to come.

“We are seeing more frequent dry and warm conditions. . . Over the last decade or so, we’re seeing these conditions more,” said Christensen, who noted that the Bow River was completely closed to angling for two weeks in 2015 due to similar conditions.

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The restrictions are the latest example of pressures being exerted on regions’ watersheds due to climate change, population growth and agricultural or industrial uses, scientists and lawmakers say.

The City of Calgary has embarked on an evaluation of its water management practices to promote conservation in the face of what it sees as growing challenges to the city’s water supply.

The rapid retreat of Rocky Mountain glaciers upstream of Calgary, which are particularly vital for bolstering water supplies in late summer and fall, is expected to continue or accelerate as the impacts of induced climate change increase. by man, scientists say.

“When we experience drought and hot days, the melting of glaciers contributes eight to 20 percent of the water supply in our rivers and that is a significant contribution,Harpreet Sandhu, the city’s watershed strategy lead, told Postmedia last winter.

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Scientists say the Bow and Elbow rivers were at half their normal levels and the lowest in 125 years last fall after the summer of 2021, which was marked by a heat dome that led to numerous high temperature records.

Warmer river water has a more severe impact on bull trout, though brown and rainbow trout are not immune, Christensen said.

The provincial government has extended the partial fishing moratorium slightly outside of ES 1 Fishing Zone and into the Rocky Mountains to deter fishermen from simply shifting their activities there and disrupting fish stocks, he said.

“Our challenge is that the Bow River is the most popular fishery and if all the fishermen were to suddenly converge on the eastern slopes, it could be unsustainable,” Christensen said.

But he said the fishing community is generally conservation-minded and has not only supported the measures, but encouraged them as concerns about climate change and sustainability have increased, he said.

The objective is not so much the application and issuance of fines, but education and deterrence, he added.

Aquatic life could see some relief soon, and Environment Canada forecasts that temperatures in Calgary will drop into the low to mid 20C range by next week.

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Twitter: @BillKaufmannjrn