Montana Fish, Wildlife & Parks fisheries biologists have completed netting efforts to remove spawning walleye from Canyon Ferry Reservoir.
As part of the reservoir's five-year lake management plan, which seeks to maintain the lake's existing trout and perch fisheries, fish managers have been attempting to limit the population growth of illegally introduced walleye by tracking and removing spawning fish from the system. The Canyon Ferry Management Plan calls for FWP to minimize the impacts of illegally introduced fish on resident populations.
Canyon Ferry, the state's most popular trout-fishing lake, is located about 20 miles southeast of Helena.
This spring, FWP fisheries crews netted 302 walleye. A total of 210, or about 70 percent of the captured walleye were stocked in other waters, said FWP fisheries biologist Ron Spoon.
"We placed 150 walleyes in Holter and 60 in Hauser lakes," Spoon said. Walleyes stocked in these reservoirs were equipped with numbered identification tags to aid in monitoring and management work on those waters. Spoon said those waters already hold walleye populations, and stressed that precautions were taken to not disrupt the balance between walleye and salmonids (trout and salmon) that exists at Holter and Hauser lakes.
Spoon said 72 walleye were donated to the food bank at God's Love, a Helena homeless shelter, six were destroyed in the nets by vandals, 10 were too decomposed for human consumption, and four large walleye remain in the possession of FWP. These fish will be aged and will likely be used for educational purposes.
Use of 3-inch Mesh Nets to Conserve Fish
Another important part of this year's work was to minimize the by-catch of nontarget species, Spoon said. In 1996, Montana State University graduate student Dave Yerk experimented with various gill-net mesh sizes to evaluate mortality trends. He determined that tightly woven 3-inch mesh netting cause the lowest level of mortality to nontarget species while still capturing walleyes. This year, the 3-inch mesh was utilized on the walleye project.
"Most of the nontarget fish we caught were carp, and we had more than two thousand of those," Spoon said. "We caught 563 rainbow trout during this effort were able to return 262 of these trout back to the lake alive."
The overall by-catch of nontarget species caught in the nets included: 2,040 carp, 563 rainbow trout, 30 white suckers, 10 burbot, two brown trout, two Utah chub, and one yellow perch. Some of the rainbow trout which did not survive netting were sent to labs for various health examinations or donated to teachers in the Project WET aquatic education program.
Spoon emphasized that the project to evaluate walleye-removal efforts is separate from the gill-net sampling which has taken place on Canyon Ferry since 1955. Gill-net sampling specifically for trout occurs in May and September and provides fish-population information. Most trout captured die in the course of the annual surveys--mortalities usually range between 300 and 600 trout. "Gill-net sampling, along with angler surveys, provide the data we need to measure the abundance and growth of trout in Canyon Ferry," Spoon said. "Gill netting is difficult work but provides valuable information."
The Canyon Ferry Reservoir/Missouri River Fisheries Management Plan has guided FWP's work at Canyon Ferry since 1993. The five-year plan will be up for review and reassessment beginning in January 1998. The public process for a new plan will be initiated and will include Holter and Hauser lakes.
"A comprehensive lake management plan will be developed for these reservoirs and it will be presented for public comments, review, and revision," Spoon said. "The overall process will link the three bodies of water as does the Missouri River and the anglers who use them.