The sustained hot weather that has crowded swimming pools and increased demand for icy drinks has been hard on some fish that rely on cool, oxygen-rich water in northeast Montana. Fish, Wildlife & Parks has verified mortality of some populations of rainbow trout and Lake Superior whitefish in Region 6.
Fish kills have been confirmed at Current and Sentinel reservoirs in southern Phillips County and at Nelson Reservoir between Malta and Saco. The mortality at Current and Sentinel involved rainbow trout; at Nelson the dead fish are lake whitefish.
“We expect to get reports of more dead trout at the smaller reservoirs and private ponds that we stock with rainbows,” says Laura Leslie, a FWP fisheries biologist based in Havre. “The lethal water temperature for rainbow trout is 77 degrees and we are certainly approaching, and occasionally exceeding, that temperature with our continued hot weather.”
Lake Superior whitefish, present in both Nelson and Fresno reservoirs, require cool, oxygenated water, and Leslie says that even in these larger reservoirs, water temperatures are exceeding lethal limits for the whitefish. Anglers have reported several hundred dead whitefish washed up on Nelson Reservoir’s shoreline.
While Fish, Wildlife & Parks plans no fishing restrictions or closures in Region 6 due to the heat, Leslie suggests that if anglers fish ponds stocked with rainbow trout, they should limit their activity to the mornings and evenings when water temperatures are lower, and they should plan to harvest fish.
“We are still relatively early in the summer to be seeing these heat-related fish kills,” says Region 6 Fisheries Manager Bill Wiedenheft. “Especially in waters that we stock with trout, we encourage anglers to harvest legal limits of fish. I would much rather that these fish go home with anglers who will consume them than to have them feed scavengers or rot on the shoreline.”
FWP encourages anglers who find dead fish to contact offices in Glasgow (228-3700) or Havre (265-6177).