Fish kill occurs in Beaver Creek below Bear Paw Dam

Staff and wire report

  Montana Fish, Wildlife and Parks reported that algae clogging the outlet at Bear Paw Dam led to the death of hundreds of fish in a stretch of Beaver Creek over Labor Day weekend.

“This was an unfortunate event and could have been worse if the low stream conditions hadn’t been reported and proper action taken,” Cody Nagel, Havre fisheries biologist, said in a release about the fish kill. “We will continue to monitor fish populations in the Beaver Creek drainage and do our best to manage this popular fishery.”

FWP fisheries personnel estimate that several hundred fish were killed in Beaver Creek from Bear Paw Dam downstream to Rotary Falls, impacting approximately a half mile of the creek, the release said.

FWP was notified Saturday, Sept. 1, that water was not apparently flowing in Beaver Creek from Bear Paw Dam on Bear Paw Lake to Beaver Creek Reservoir.

FWP personnel found the water outlet structure at Bear Paw Dam was clogged with dense amounts of algae that had been present in the reservoir. The gates were opened to increase outflows and flush out the algae that had accrued, releasing large amounts of both algae and warm, poorly oxygenated water into Beaver Creek immediately below Bear Paw Dam.

FWP reports that the combination of no apparent stream discharge due to the algal obstruction, along with low dissolved oxygen present in the water released with the algae, likely contributed to the fish kill. However, as of Friday, no one factor has been identified as the primary source of the fish kill.

The last two summers have been very hot and dry, which has led to several large algal blooms in both Bear Paw Lake and Beaver Creek Reservoir. Algae is typically visible on the shoreline and surface water, however, the recent cool weather shifted layers of water in Bear Paw Lake. That pulled a large amount of the algae present on the surface and within the surface water column straight to the bottom, which led to the outlet structure being clogged.

The fish kill in the stretch was severe but wasn’t a complete kill. Sept. 5, fisheries crews electrofished approximately 800 feet of Beaver Creek between Bear Paw Dam and Rotary Falls.  Crews observed at least two rainbow trout and saw decent numbers of white suckers, longnose dace, mountain suckers and mottled sculpin.

“Trout densities will remain low in this stretch for some time,” Nagel said, “but will likely soon re-populate from fish moving back upstream from Beaver Creek Reservoir and downstream from Bear Paw Lake.”