Renowned as the best kokanee salmon fishery in Colorado, Blue Mesa Reservoir has struggled recently to maintain its kokanee salmon population. The primary 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 conducted 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. 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.
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.