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Angling restrictions in heat-stressed Bow, other rivers take effect Saturday

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Provincial officials are hoping to reel in the impacts on heat-stressed fish in the Bow and other southern Alberta rivers by imposing angling restrictions that start Saturday.

But a spokesman for a leading conservationist/outdoor enthusiast group said the measure doesn’t go far enough to address to address a more widespread impact of climate change and water management.

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As of 2 p.m. and extending to midnight daily, angling will be forbidden in the Bow and other rivers in south and southwestern parts of the province to give a break to fish stressed by low water levels that have led to elevated temperatures.

The angling restrictions — impacting the Bow River East Slopes Fishery Management Zone 1 and the St. Mary River below the St. Mary Reservoir — are expected to last through Aug. 31.

That’ll encompass the Bow River from Banff to Bassano, “and everything north of 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 drove the temperature of the Bow River to 20 C for five consecutive days. The threshold needed to make such a decision is reached when water temperatures exceed 20 C for three or more consecutive days, and when the flows in the Bow are below the 25th water flow percentile for four or more days.

“The lower water level makes the temperature warm even quicker and makes the fish more vulnerable,” said Christensen.

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Warmer water holds less oxygen for the fish, who are further stressed by angling, “so we’re trying to halt that activity during the part of the day when it’s particularly hot,” he added.

It’s an action taken unexpectedly, he said, after last winter’s heavy snow pack and a later melt.

But he said the current lingering hot spell has seen river flows drop with little water from the mountains replenishing it — a trend that’s likely to continue in years to come.

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

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

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

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The rapid retreat of Rocky Mountain glaciers upstream from Calgary, which are particularly vital in bolstering late summer and autumn water supplies, is expected to continue or quicken as the impacts of human-induced climate change mount, say scientists.

When we experience drought and hot days, glacier melt contributes eight to 20 per cent of the water supply in our rivers and that’s a significant contribution,” Harpreet Sandhu, the city’s watershed strategy leader, told Postmedia last winter.

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.

The province should impose the partial moratorium on more of the province, said Darryl Smith, the Alberta Fish and Game Association’s provincial fish chair.

“We believe these issues should be addressed on a province-wide fashion if the goal is to reduce fish mortality,” said Smith.

He said river levels are low in parts of Alberta far to the north of the Bow River watershed, such as in the Peace River region – a situation that’s worsening with climate change and increasing draws on rivers for human use.

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“We should all be concerned – the cold water ecosystem we don’t have a lot of in Alberta, it’s a shrinking resource,” said Smith.

He noted angling moratoriums are realities in B.C. and in U.S. states, the latter which have been especially hard-hit by severe drought conditions scientists say have been worsened by climate change.

The warmer river water has a more severe impact on bull trout, though brown and rainbow trout aren’t immune, said Christensen.

The provincial government has extended the partial fishing moratorium slightly outside the Fisheries Zone ES 1 and into the Rockies to deter anglers from simply shifting their activities there and disrupting fish populations, he said.

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

But he said the angling community is generally conservation-minded and has not only supported the measures, it’s encouraged them as concerns over climate change and sustainability have risen, he said.

The goal isn’t so much enforcement and ticketing, but education and deterrence, he added.

Aquatic life could be seeing some relief soon, with Environment Canada  forecasting temperatures in Calgary to drop into the low-to-mid 20 C range for next week.

BKaufmann@postmedia.com

Twitter: @BillKaufmannjrn

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