06/30/2015 10:02 EDT | Updated 06/30/2016 05:59 EDT

Sport fishing ban urged by conservationists as temperature in B.C. rivers rise

Conservationists, First Nations and angling associations are calling for sport fishing restrictions as the prolonged heat wave and drought in B.C. spike temperature in rivers and lower water levels.

The Cowichan River on Vancouver Island has become so depleted, the Cowichan Tribes have closed it to fishing by its members.

The group The Friends of the Cowichan River is also calling on the province to restrict sport fishing to protect trout, steelhead, and salmon. The province, however, has yet to respond.

Pat George, who chairs the conservation committee for the Haig-Brown Fly Fishing Association, says oxygen levels go down when river levels are lowered. Reduced levels and the heat lead fish to try and survive by going into deeper, cooler pools.

The fish are already so stressed out that when anglers target them at the pools, they don't survive after being released, George said.

"A lot of anglers don't realize it, with the equipment we've got today for fishing, they have a tendency to play the fish too long, and if they release the fish, it really stresses out the fish and the mortality rate just increases," he told B.C. Almanac.

Scott Hinch, a professor of fisheries conservation at the Pacific Salmon Ecology and Conservation Laboratory at UBC, expects temperatures will continue to rise over the summer.

The Fraser River, for example, could peak at 19 or 20 degrees, and that, plus low flows, could impact whether spawners could get to spawning grounds, he said. 

"By the time you get to 20 degrees, many [fish] are suffering mortality because they're either suffering from low energy reserves — because they have to work a lot harder when temperatures are higher and they have a finite amount of energy they're bringing with them," he said.

"We also see a prevalence of diseases taking over at these higher temperatures, and just generally, physiological stress kicks in, and that exacerbates these other things, so a lot of the work we've done shows that when you get those temperatures, these fish don't do so well in terms of their return migration."

Listen to the full interview: Drought-stressed streams impacting B.C. fish