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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

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. But recent surveys estimated that the population dipped to less than 200,000. CPW biologists, however, 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. 

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. CPW is stocking 3.5 million kokanee and is removing about 1,300 lake trout per year. Biologists also believe that higher water levels in the reservoir during the last two years -- and likely again for 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.

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 off the average of more than 6 million. About 4 million eggs must be collected to produce the 3.5 million kokanee fry that are needed to stock Blue Mesa every year. Low-egg harvest also creates a larger problem because Blue Mesa, traditionally, has produced the significant number of eggs needed 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 10 fish to five fish, but the possession limit has been maintained 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 continue to be liberal for lake trout, although one change is aimed at allowing 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 previously. 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, help to improve the survival of kokanee. Lake trout are very tasty and very nutritious. 

The challenges of reservoir fisheries management

A critical factor in understanding the Blue Mesa fishery is 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, making 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 significant numbers of this fast-growing and highly valued species. Trophy lake trout are dependent on a healthy kokanee population. Continued low kokanee abundance suggests that the reservoir continues to be out of balance. There are no quick fixes; balancing the fishery at Blue Mesa is a long-term project.​