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Blue Mesa Reservoir Fishery Management
Blue Mesa Reservoir Fishery Management
Kokanee salmon under water

​​​​​​​​2016 Update on Blue Mesa Reservoir Activities 

Recent sonar surveys show an increase in kokanee salmon population.

Background

Renowned as the best kokanee salmon fishery in Colorado, Blue Mesa Reservoir has struggled recently to maintain its kokanee salmon population. The primar​y reason for the decline is predation by lake trout. In the early 2000s, the kokanee population at Blue Mesa Reservoir numbered more than 1 million. Unfortunately, recent surveys estimated that the population dipped to less than 200,000. CPW biologists also took note of some good news from sonar surveys in 2015, which showed a population of 400,000. More sonar surveys will be conductedBiologist squeezing salmon eggs this year to determine if the trend is continuing. 

CPW in Action

Colorado Parks and Wildlife aquatic biologists continue to work diligently to rebuild the population through increased stocking of kokanee and continued removal of lake trout. Each year, CPW stocks 3.5 million kokanee and removes about 1,300 lake trout. Biologists also believe that higher water levels in the reservoir during the last two years -- and likely again this year -- will help the fish. With more water in the reservoir, this open-water species gains more habitat, distributes more widely, and should be less vulnerable to predation.

Effects on Regulations

The decline in kokanee has also led to a decline in the number of eggs taken during the annual spawning run. In 2015, CPW biologists harvested just 2.1 million eggs, well below the average of more than 6 million. About 4 million eggs must be collected to produce the 3.5 million kokanee fry required to stock Blue Mesa every year. Low egg harvest also creates a larger problem because Blue Mesa has traditionally produced the most significant number of eggs to supply up to 25 other reservoirs throughout Colorado. Fortunately, other waters produced enough eggs to make up the difference for stocking this year. 

Angler with 28 pd mackinawA regulation change for kokanee this year might help to improve future kokanee egg-take. The daily bag limit for kokanee has been reduced by half from ten fish to five, but the possession limit remains at 10. The change was made at the urging of anglers whose catch rates have declined substantially in the last few years. 

Bag and possession limits remain liberal for lake trout, although one change aims to allow more “trophy sized” fish to grow in the lake. Anglers can now keep only one fish per day that is bigger than 32 inches, down from 38 inches. Other than that, anglers can keep all the lake trout they catch. CPW biologists explain that smaller lake trout, because of their numbers, consume the most kokanee. The average size of the lake trout caught by anglers is 19 inches. 

CPW encourages anglers to keep all smaller lake trout they catch. Anglers can play a large role in keeping lake trout populations in check and, in turn, improving the survival of kokanee. Plus, lake trout are very tasty and nutritious!

The unique challenge of reservoir fisheries management

A critical factor in understanding the Blue Mesa fishery is recognizing that the reservoir is a human-made impoundment. The biology of a reservoir is far different than a natural lake. Managing a fishery in this type of environment is complex and challenging. Neither kokanee nor lake trout are native to Colorado and they did not evolve Raising kokaneetogether, which makes management of these two species difficult.

Kokanee, however, are the key species for maintaining a variety of angling opportunities in the reservoir. Kokanee provide opportunities for anglers to catch and harvest this fast-growing and highly valued species. Trophy lake trout are dependent on a healthy kokanee population. Continued low kokanee population suggests that the reservoir is still out of balance. There are no quick fixes; balancing the fishery at Blue Mesa is a long-term project.​