Blue Mesa Reservoir is renowned as one of the best kokanee salmon fisheries in the United States. Since fish stocking began at the reservoir in 1965, developing and maintaining the kokanee fishery has been the major priority for Colorado Parks and Wildlife. Kokanee continue to provide great fishing opportunities at the reservoir, but maintaining overall kokanee numbers has become difficult due to increased predation of kokanee by lake trout.
A decade ago the kokanee population at Blue Mesa numbered more than 1 million. But the most recent surveys by Colorado Parks and Wildlife biologists show that the current population is about 165,000, down from an estimated 290,000 fish in 2012.
Colorado Parks and Wildlife is working aggressively to rebuild the kokanee population by stocking 3.5 million kokanee annually and by continuing work to reduce lake trout predation on kokanee. We're also calling on anglers to help by harvesting the lake trout they catch.
Kokanee egg-take operations from the Blue Mesa kokanee run again provided a significant proportion of the state's eggs in 2013, with a total of 7.5 million kokanee eggs collected. Although the total egg-take was down from record numbers taken in 2012, it was enough to ensure that Blue Mesa and 25 other reservoirs in Colorado will be stocked with kokanee this year.
Drought conditions continued into 2013, but conditions improved following rain and snowfall in the late summer and fall. Late season precipitation did result in some improvement in storage levels in the reservoir. Improved snowpack in 2014 makes it likely that reservoir levels should be significantly improved this summer.
Significant algae blooms occurred in the late summer in 2013. Decomposition of these blooms in early September did affect habitat available for fish as oxygen levels became very low in portions of the Cebolla and Sapinero basins. Some mortality of adult kokanee was documented; these fish may have been more susceptible to low oxygen impacts as they were preparing to spawn. Conditions began to improve by mid September, with recovery of reservoir oxygen levels occurring in most areas of the reservoir by late September.
Lower kokanee population estimates in 2013 indicate that continued reduction in the lake trout population is necessary to ensure that kokanee numbers improve. The lake trout population can be maintained at a reasonable level through a combination of angler harvest and lake trout removal work. If the population goes unchecked lake trout will eventually overwhelm kokanee.
Reduction and eventual maintenance of lake trout population size at desired levels will be best achieved through a combination of lake trout harvest by anglers and removal by Colorado Parks and Wildlife staff. Fish populations will be monitored over time to assess whether harvest and removal are being effective; but it is expected that removal work will continue indefinitely.
Anglers do catch a significant number of lake trout and Colorado Parks and Wildlife continues to encourage anglers to harvest this species. As angler harvest is about three times the number that Parks and Wildlife staff remove annually, angler harvest is an important part of the solution at Blue Mesa. The main reason is that anglers are on the water in much greater numbers throughout the year: about 60,000 anglers fish at Blue Mesa annually.
Angler harvest of lake trout will make the largest impact on kokanee recovery efforts. Lake trout under 26 inches in length are most abundant and therefore consume the most kokanee. There are no bag or possession limits for lake trout measuring less than 38 inches.
Smaller lake trout are often caught by anglers pursuing other fish species. In fact, 84 percent of the lake trout caught are under 22 inches. Lake trout make excellent eating and are very nutritious. Anglers can, literally, fill their freezers with this delicious fish.
By reducing the lake trout population, overall kokanee catch rates for Blue Mesa anglers will improve. But there's also something in this for lake trout anglers – as smaller fish are removed a greater number of lake trout will grow to trophy size.
During the last five years, biologists have removed about 6,000 lake trout from the reservoir. About 1,300 lake trout were removed in 2013. All lake trout over 32 inches in length were returned to the water to maintain trophy lake trout angling opportunity. Of the 1,300 lake trout removed, 208 were transferred to Twin Lakes to supplement lake trout populations at that water. The remainder were filleted and donated to anglers. Biologists hope to remove up to 2,000 lake trout from Blue Mesa Reservoir in 2014.
Every year during fall, kokanee swim 20 miles up the Gunnison and East rivers to the Roaring Judy hatchery where they are spawned. Colorado Parks and Wildlife have taken steps to ensure that most of the spawning kokanee swim into the hatchery canal where the eggs are harvested.
Biologists also work to protect the fish in the spring when young kokanee, about 2 inches in size, are released from the hatchery. On the day the fish are released, local landowners and Colorado Parks and Wildlife work cooperatively to close or screen irrigation ditches along the East and Gunnison rivers to prevent the tiny fish from leaving the main channel, thus assuring that more young fish make it to the reservoir.
Parks and Wildlife has also bolstered the population of kokanee in the reservoir by releasing more fish in the spring. During each of the last five years, the agency has increased the number of fingerlings released into the reservoir by about 500,000, bringing the total number stocked annually to about 3.5 million.
Stocking more and more fingerlings, however, is not a long-term solution. Fish production space is limited and egg take can vary considerably from year to year, and will likely decline in some years.
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 the species did not evolve together. Consequently, the predator-prey relationship is not natural.
Kokanee, however, are the key species for maintaining a variety of angling opportunities in the reservoir. Trophy lake trout are dependent on a healthy kokanee population. Continued low kokanee abundance 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.
All types of fishing at Blue Mesa Reservoir are important to the economy of Gunnison County. Based on years of surveys, kokanee anglers are the most active at the reservoir. In 2004, a study estimated that fishing at Blue Mesa generated an economic impact of about $8 million per year. Of that amount, 80 percent of the spending -- about $6.4 million -- came from kokanee anglers. People throughout Colorado and the United States travel to Blue Mesa to fish for this freshwater salmon species.
Beyond the immediate impacts in Gunnison County, kokanee production at the reservoir is critical to sport fishing throughout Colorado. Blue Mesa provides an average of 60 percent of the kokanee eggs needed to stock fingerlings into lakes and reservoirs throughout the state. The overall annual economic impact of kokanee salmon fishing in Colorado is estimated to be at least $29 million.