Additional kokanee salmon collection sites will be implemented at Cheesman Reservoir in Douglas County, and Wolford Mountain and Shadow Mountain reservoirs in Grand County.

"Expanding our egg-collection effort is necessary this year to improve our chances to collect enough eggs to sustain the state's kokanee salmon populations," said Greg Gerlich, DOW fisheries chief. "We are hopeful that we can still meet objectives by expanding to these other locations."

The DOW collects approximately 11 to 12 million kokanee eggs annually to meet fishery management goals and to maintain the state's kokanee salmon populations. Since natural reproduction is limited, sustainable kokanee populations are dependent on fish stocking programs and eggs collected from a limited number of brood lakes each fall.

Only 6.9 million eggs have been collected so far this season. While egg-takes remained average to above average at most brood reservoirs (Vallecito, McPhee, Williams Fork and Granby), DOW aquatic biologists attribute this year's egg deficit to a steep decline in the kokanee salmon population at Blue Mesa Reservoir.

"We've been seeing a substantial decline in the kokanee populations at Blue Mesa for the last several years," said John Alves, DOW senior aquatic biologist. "Blue Mesa provides half of the eggs that are used to sustain kokanee populations throughout Colorado, which is why a declining kokanee population in the reservoir is a considerable threat to the management of our fisheries."

Historically, 5 to 8 million kokanee eggs are collected annually from Blue Mesa. This year, a meager 2.5 million eggs were harvested, leading biologists to expand egg-collection to alternative locations.

"Our strategy over the years is to have additional waters where we can collect fish to keep the program going when efforts at primary brood waters are unsuccessful," said Gerlich. However, this places a considerable strain on our resources and is much less efficient."

Since fish stocking began in Blue Mesa Reservoir in 1965, developing the kokanee salmon fishery has been the major priority of the DOW. Biologists believe a growing lake trout population is the primary cause for the declining kokanee population in the reservoir.

"Kokanee spawning and egg-collection efforts have remained stable in reservoirs where lake trout predation is not a factor," said Gerlich. "This is why it's imperative to establish a better balance between the lake trout and kokanee populations at Blue Mesa."

This fall, the DOW began a project to remove some of the lake trout, which reproduce naturally at Blue Mesa, from the reservoir. The removal project will continue each year until DOW aquatic biologists determine that predation on kokanee has declined to where the salmon population is no longer threatened. That decision will be aided by spring survey research that will be done by the DOW and by researchers from Colorado State University.

News Source: Colorado DOW - Nov. 16, 2009