Montana Fish Wildlife & Parks (FWP) fisheries crews began implementation of the South Fork Flathead Westslope Cutthroat Trout project with rotenone treatments of Black and Blackfoot Lakes in the Jewel Basin. These lakes contained hybrid trout, which threatened the pure westslope cutthroat trout downstream in the South Fork of the Flathead River. These will be the only lakes treated this year. FWP Fisheries Biologist Matt Boyer reports that it is likely that a complete kill of the hybrid trout was obtained. Boyer noted that Black and Blackfoot lakes would be restocked with westslope cutthroat trout this coming summer.
Black Lake: Fisheries crews completed the rotenone project on Black Lake in the Jewel Basin Hiking Area on September 28. The project went very well and it appears that a very effective kill of the hybrid trout was obtained.
Equipment, including a boat/motor, rubber raft, rotenone barrels, and application gear, was flown in by helicopter and sling on September 25. Weather was unsuitable for the air-drop of rotenone on September 26. On September 27, a single engine air tanker (SEAT plane) dropped 1,260 gallons of rotenone in three drops into Black Lake. Crews then distributed 210 gallons of rotenone using a boat/motor with a nozzle set-up. Crews also applied rotenone to a small lake just downstream from Black Lake. A number of drip stations were set up and operated for 8 hours on small tributaries around Black Lake and in the stream below the lake.
Fish began dying almost immediately upon application of the rotenone. Based on observations along the shoreline and across the lake surface a very thorough kill was obtained. Trout from fingerling size up to 18 inches were noted. The majority of fish sank quickly to the bottom of the lake. Fish along the shoreline were collected and transported offshore to be sunk to the bottom.
On September 28, all equipment, barrels, and tools were sling-lifted out of the area. Crews walked in and out during the project. Visitors to the Jewel Basin Hiking area adhered to the trail closures and no members of the public were in the area during the project.
Blackfoot Lake: Fisheries crews completed the rotenone project on Blackfoot Lake in the Jewel Basin in a single day on October 8. Treatment included boat application of 65 gallons of rotenone lake-wide. Three drip stations and backpack spray application were used to distribute an additional two gallons of rotenone in three inlet tributaries. A relatively small amount of rotenone was needed for this lake due to its small water volume.
Four helicopter flights transported the boat, rotenone barrels, and other equipment to the site.
Blackfoot Lake supported one of highest levels of rainbow trout hybridization in the South Fork Flathead drainage. Hybrid trout ranging in size from fry to 18 inches were noted. Many fish sank to the bottom after treatment. Other fish were gathered and sunk. These fish will provide nutrients to the food chain and a basis for the re-establishment of a westslope cutthroat trout fishery beginning next summer.
Future Plans: This summer, additional cutthroat trout genetic samples were collected to help guide management in future years. If some of these lakes have responded to past stocking of pure westslope cutthroat, it is possible that rotenone treatment may not be needed. Current plans call for treatment of about two lakes containing hybrid trout each year over the next nine years.
FWP will hold an annual meeting in May to provide an update on the project and plans for 2008. FWP’s website: http://fwp.mt.gov/regions/r1/wctproject/default.html contains more detailed information on the project. Soon, photos and video of the Black and Blackfoot lakes treatments will be available on the site.