New management plans for reservoirs seek to balance predator and prey

Anglers enjoy the last rays of a mild September day while fishing Harvey Gap Reservoir. A proposed change ion fisheries management would include tiger muskies in the reservoir’s diverse mix of fish.

Ten years ago, rare was the angler at Rifle Gap Reservoir with a yellow perch in his creel.

Back then, the dark-striped, fast-breeding interloper was little more than another rumor in what was at the time among the state’s best cool-water trout fisheries.

However, creel surveys last year indicate anglers caught nearly 90,000 perch from Rifle Gap Reservoir in 2009, combining results from both the open-water and the ice-fishing seasons.

That prodigious number, which means two of every three fish caught last year from Rifle Gap was a yellow perch, at first surprised biologists but now leaves them wondering what the future holds.

“Initially, I think I was surprised at that number,” said Lori Martin, area fisheries biologist for the Colorado Division of Wildlife. “But after seeing how many folks are out there targeting perch and seeing what the perch population is like, I don’t think I’m so surprised anymore.”

Today, Martin said, “We are biding our time in relation to the perch.”

But while perch are the elephant in the living room, they aren’t the only change at Rifle Gap.

Today, anglers try their skill for 10 different species, among them rainbow and brown trout, northern pike, smallmouth bass, black crappie, walleye and yellow perch.

The mix makes management a balancing act.

Jump a few miles east to Harvey Gap Reservoir, which has challenges of its own.

There, northern pike are dominating a fishery that includes trout, perch, bluegill, bass, channel catfish and black crappie.

But it’s anglers, and today’s move toward catch-and-release fishing, that really throws off management plans.

Even though angler hours have more than doubled since 1987, creel surveys indicate the number of fish kept has fallen off dramatically.

“Fishermen have really fallen for catch-and-release, to the detriment of many fisheries,” said Lynn Ensley, executive director of the Colorado Sportsmen Wildlife Fund. “That makes it a lot tougher to properly manage a fishery.”

With an eye on balancing angler desires and still maintain some balance between predator and prey, the Division of Wildlife is developing new lake management plans for the two impoundments.

“We’re at the point we want to hear from anglers while we look at options for our management decisions,” Martin said.

The public comment period has been extended through this month. The proposals can be seen at

It won’t be easy forging a policy. In addition to anglers and water districts, plans for Rifle Gap must comply with federal endangered species regulations since that reservoir leads to the Colorado River.

Harvey Gap already has a management plan approved by the Fish & Wildlife Service, Utah and Wyoming, all parties to the river fish recovery program.

But for any changes in the present plans to be successful, angler assistance is a must, Martin said.

“If we’re looking at using tiger muskies to control pike at Harvey Gap, we also have to rely on anglers to harvest pike or whatever predator we have,” she said. “You need some level of predator control or you’re going to have problems.”

But Ensley cautioned, “I don’t know that they can count on anglers” to control fish populations.

He suggested a regulation allowing one trophy sized pike or muskie and several smaller fish.

Martin said something similar is proposed for both reservoirs although the “mechanical removal” of pike could be necessary if anglers don’t do the job.

As for perch taking over Rifle Gap, the division is looking to prevent that by introducing tiger muskie or saugeye (a sterile cross between walleye and sauger) as predators.

Approximately 40,000 rainbow trout are stocked each year in Rifle Gap, but Division surveys indicate that while the catch in 2009 nearly doubled that of 1987, the number of trout kept by anglers is less than a third of what it was 20 years ago.

That’s either through choice (catch and release) or other fish (northern pike, walleye) are eating the rainbows.

Martin says the declining rainbow harvest and the skyrocketing perch haul leaves the division with few choices.

Left unchecked, yellow perch could turn Rifle Gap into the latest version of Crawford Reservoir a decade ago.

People caught buckets of tiny perch and it wasn’t until northern pike started putting a big dent in the perch numbers that the Crawford fishery regained a sense of normalcy.

Compounding any fisheries plans are the fluctuating water levels at both irrigation-oriented reservoirs.

“Something has to be done,” said Ensley, who approves the Division’s plan to use walleye in Rifle Gap as a predator on the perch.

“Whatever they do, it’s going to be a hard balancing act,” he said.


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