Nicola River, Coldwater River and Spius Creek were temporarily closed to recreational fishing Monday, Aug. 29.
Steve Maricle, fisheries biologist with the Ministry of Forests, Lands and Natural Resource Operations, said the closure is necessary to protect trout and salmon from health risks associated with rising water temperatures.
Temperatures have been falling in the region, but the move is partly a precautionary measure related to low numbers for chinook and bull trout.
"The reality is, we can't predict what will happen in September," he said. The usual problem of low flows was compounded by an early melt. Small glaciers and snowfields in the region, which used to sustain flow levels during summer, are almost gone.
"It seems to be almost the norm," to the extent where the late-season closure could become a permanent measure.
"You're not affecting a lot of fishermen at that time, but those fishermen can do a lot of damage," he added. As waters recede, trout are inclined to congregate in pools, making them more vulnerable.
When stream temperatures rise above 20 C, the mortality rate of catch-and-release trout increases, the ministry noted.
Mirroring a federal steelhead closure on the same waters, the closure will remain in effect until further notice.
Under the federal Fisheries Act, the province is responsible for non-salmon freshwater fisheries, including sea-run steelhead, cutthroat and Dolly Varden.