Mesa County, Colorado — The complete draining of a western slope reservoir is underway in an effort to rid the small lake of northern pike before the illegally introduced predators devour four species of endangered fish that have been recovering there for more than three decades, CBS Denver reports.
The northern pike were first spotted at the Mack Mesa Reservoir by anglers last fall, according to the Colorado Parks and Wildlife.
CPW officials conducted an immediate sample count and removed several adult northern pike. Additional fish were later discovered during a time when northern pike are known to spawn.
"Northern pike are a voracious predator that cannot be managed in Mack Mesa," explained Ben Felt, CPW's aquatic biologist for the Grand Junction area.
CPW officials suspect someone illegally transported and released northern pike into Mack Mesa. "Someone trying to selfishly create a place to catch their own favorite fish," the agency stated in a press release.
"Movement and stocking of fish into Colorado waters by private individuals without CPW approval is against the law," said Area Wildlife Manager Kirk Oldham. "In addition, CPW does not stock northern pike in western Colorado waters because the species is a significant threat to native fish that are found only in the Colorado River basin."
A three-state pact, the Upper Colorado River Recovery Program, was initiated in 1988 to recover humpback chub, razorback sucker, bonytail and Colorado pikeminnow, four fish reported to be on the brink of extinction at that time. Mack Mesa is part of that network.
Efforts to drain Mack Mesa began earlier this month. It will be emptied until all the fish in it can be caught. The pike will be eliminated while the other species will be transferred to nearby Highline Lake.
Mack Mesa will be re-stocked with trout, largemouth bass, black crappie, bluegill, and channel catfish.
"We hope to get ahold of some large brood fish to make sure that Mack Mesa will be immediately fishable by anglers in May," said Highline Lake State Park Manager Alan Martinez. "This disruption for anglers is unfortunate and we hope anyone who loves Mack Mesa will help us keep an eye out for anyone who might illegally move fish here or anywhere else."
Officials considered closing Mack Mesa for the duration of the fishing season but ultimately decided not to for several reasons, including a full closure "being too punitive to the many responsible anglers that enjoy the lake."
However, any problems that arise in the draining and removal operation may result in that full closure of the lake to fishing or the suspension of stocking any fish in Mack Mesa.
"This is an unfortunate situation, and one that CPW would prefer not to be in," said Northwest Region Senior Aquatic Biologist Lori Martin.
Both Mack Mesa and Highline Lake are part of Highline State Park and are located about 10 miles east of the Colorado-Utah border, north of Grand Junction, in far western central Colorado.