As Game and Fish red shirts pulled into the launch at dusk, Deaver Reservoir fishermen were few. Those left were working hard for bites, but it was still early. Walleye move to the shallows after dark.

The department biologists brought a 6,500 watt generator powering a 240-volt system to assist in their after dark catch. Not many fish in their path would escape the pulse direct current running to a boom resembling a robotic octopus for the annual count of walleye in the popular fishery.

“Our objective is to catch at least 80 walleye over the 10-inch mark,” said Jason Burckhardt, Cody Region fisheries biologist as he swatted at unwanted flying pests.

A light breeze kept most of the mosquitoes off balance during their assault on shore as Burckhardt went over safety regulations. The department has been aggressively managing the reservoir for walleyes for the past 20 years. “Last year [the population] had dipped a little bit,” Burckhardt said before the test began.

“The numbers vary a little depending on the netters as well,” he explained, probably apprehensive about his newest inexperienced netter. This stout Tribune reporter was roped into duty when a game warden had a scheduling conflict.

Each netter averaged a little more than three fish a minute during the 60-minute test. Excitement was high as several beautiful walleye were netted. All looked healthy – even those less than 5-inches – but only walleye 10-inches or bigger were counted in the operation.

The math is based on an equation called Catch Per Unit Effort. The team worked the banks of the reservoir pulling in hundreds of fish - nearly 113 were walleye making the 10-inch benchmark. This was well over the benchmark of 80. There were several minutes of relaxation with no fish. Then there were moments where fish came too fast and a few were missed.

“Ten percent of the water holds 90 percent of the fish,” Burckhardt said.

The electrical current causes the walleye’s muscles to contract, and they swim toward the boom. Netting them isn’t terribly hard, other than managing the specially designed nets with ten-foot poles against the current. Sometimes multiple walleye need to be caught at a time. The hardest part is emptying the net quick enough to get back to pulling in more walleye.

The wide, flat-bottomed aluminum boat is equipped with powerful lights and illuminated an underwater habitat rich with what shore fishermen would call snags. Interestingly, no expensive lures were seen in the hour test. Walleye weren’t the only fish caught that night. Some beautiful pan fish were pulled in, as well as at least one fish of special interest.

Game and Fish seasonal fisheries tech and University of Wyoming graduate student Luke Ruthven kept his eyes out for brook sticklebacks. The tiny invasive species with spines on its back is the subject of his master’s thesis. They most likely made their way into the reservoir in a bucket of bait.

The brook stickleback is native to eastern states, but has been introduced into at least 16 states outside its native range – primarily as a result of baitfish introductions. They’ve been found in several drainages throughout Wyoming, including Shoshone River drainages like Deaver Reservoir.

The species compete with and negatively affect other fish species. And studies have shown they also harm waterfowl due to the species’ affect on zooplankton biomass and abundance. Brook stickleback are known to forage for other fish species’ eggs, which might also hurt fish populations, resulting in reduced fishing opportunities.

Ruthven’s studies may help understand the effects of yet another invasive species in the Cowboy state. Deaver Reservoir allows for the use of minnows, unlike many fisheries in the state, and may be the source of the species in the area, Ruthven said.

If found in a bucket of bait, know that it is illegal to possess or transport the species. But in Deaver, even young sucker fish are prey for the toothy walleye.

“We’re going on 20 years of managing it as a walleye fishery. Most folks, including myself, are amazed about the quality of a fishery this reservoir is. It’s a tiny 30-acre lake and we’re producing some decent fish,” Burckhardt said.

The data shows clearly that when the Game and Fish implemented the reduced limit, going from a six-fish limit to three, populations have made a “dramatic increase,” Burckhardt said. That translates to great walleye fishing, this year better than most. Not counting those missed by the netters, a total of 185 walleye were counted in an hour of electrofishing. Most of the walleye captured were between 10 and 15 inches. The test far exceeded the objective of 80. The largest we sampled was 21.9 inches and weighed 3.56 pounds, Burckhardt reported.

“There are larger ones in there,” he said.