War on walleye: Game and Fish turn up heat on unwanted species

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In any other fishery, fat walleye would be a source of pride. But in Buffalo Bill Reservoir, they’re a scourge — and the fight to rid the important trout habitat of the voracious, toothy predator is heating up.

On Friday morning, Jason Burckhardt led a team to retrieve seven 300-foot monofilament gillnets deployed near the base of Cedar Mountain. It was a rare day with mild winds along the North Fork Highway. While crew members pulled up to the first set of bright orange buoys, Burckhardt — Cody Region fisheries biologist for the Wyoming Game and Fish Department — was anxious.

He steadied the boat, keeping it from the nearby rocky shore while his crew hooked the first line.

“Our catches have been down considerably from this time last year,” Burckhardt said as fisheries technician Mark Komoroski and volunteer Kris Cooper pulled in the long net by hand. The first net brought no walleye.

But the crew’s fortunes were about to turn. The next sets of nets progressively got better. Smiles among the crew grew broader with catches of fat female walleye, some ripe and dripping eggs. The previous night, electrofishing crews brought 69 walleyes, but most were males.

By law, all walleye caught in the reservoir must be immediately killed, but catches of males aren’t nearly as important as females, Burckhardt said.

“You’re not going to limit a population by removing the males,” he said while navigating a boat near the shore of the 8,300-acre reservoir.

“Walleye are a sought-after fish in most places. And there are places that we actively manage for walleye,” Burckhardt said. “This is just not one of them.”

Mesh size on the nets were selected to catch only the largest walleye and to reduce the number of trout in the net. Most snagged trout were still feisty and released unharmed. There is some mortality, with each dead fish measured and recorded. The goal is to save every non-targeted species, but considering a single breeding-age female walleye has consumed thousands of rainbow and cutthroat trout fry in its life, it’s worth the small amounts of trout mortality, Burckhardt said.

This is the second year of the gillnetting operation. Prior to netting, the teams had only been electrofishing for the species.

“You can be very selective with electrofishing, which is its benefit — not having any issues with bi-catch,” Burckhardt said. “But the down side to electrofishing as it relates to this walleye effort is we were only catching males. Gillnetting is essential to this project.”

Each breeding-age female carries about 50,000 eggs. If left unchecked, the population of walleye would grow exponentially, crashing the reservoir’s trout population — including northwest Wyoming’s native cutthroat trout.

The department recently enlisted the help of Montana State University grad student Daniel Kaus. Kaus’ study showed electrofishing was ineffective in reducing walleye populations. He contends a combination of must-kill regulations for anglers and gillnetting could be effective in crashing the population. His study showed the walleye population would continue to grow for the next five years, but then would decrease dramatically. Still, even after walleye populations have tanked, the fight will need to be continued.

“[The fight] needs to be continued in perpetuity,” Burckhardt said at a recent meeting announcing the results of Kaus’ study.

Otolith (ear bone) studies proved the walleye illegally introduced to Buffalo Bill Reservoir came from Deaver Reservoir, a popular walleye fishery stocked by the Game and Fish. The illegal stocking will cost the department millions in resources and labor in the fight.

Not everyone supports the department’s gillnetting efforts. Some are opposed to the idea because of the bi-catch, which on occasion includes trophy lake trout. Many are vocal in their opposition, Burckhardt said.

“Even if they don’t support our efforts, they understand what we are doing out here,” he said. “The science is pretty clear, if we have a robust population of walleye, they’re going to consume a very large portion if not almost all of the juvenile that come and restock this reservoir.”

All of the trout in the reservoir are naturally spawned in the North Fork of the Shoshone River. Buffalo Bill is the only reservoir in the state not stocked by the Game and Fish. The last year it was stocked was in 1995.

The department has decided to use volunteers to assist in the gillnetting effort. Cooper, a Clark resident who works for the Park County Road and Bridge department in Powell, is just one of many volunteers willing to help. Beyond providing much needed help, adventure on the lake and a few walleye filets are the sole payoffs for volunteers.

Several of the walleye brought in went home with project volunteers. Others are donated to raptor programs including the Draper Natural History Museum at the Buffalo Bill Center of the West and Ironside Bird Rescue.

Back at the Game and Fish’s Cody office, scores of healthy males, dwarfed side by side with ripe females, were aligned in size categories awaiting the removal of their otoliths. Electrofishing on Thursday night and retrieval of gill nets Friday morning resulted in capturing almost 70 males and just under 20 females.

Fisheries biologist Travis Neebling, the department’s reservoir specialist, will do the tedious work of testing the otoliths. While the age of a walleye can be determined by checking scales, testing the ear bones is a much more precise way to check age, Neebling said. Each tiny bone is sliced thin and viewed by microscope. Otolith isotopes can also be tested for clues to where the fish originated.

The delicate operation of removing the otoliths will shed a lot of information on the walleyes’ lives. Previous studies of otoliths showed walleye were illegally stocked in the reservoir multiple times about 15 years ago. The crime was detected roughly a decade ago.

By the end of Friday, water temperatures were reaching optimal spawning temperatures and the spawn was in full swing at the reservoir. Crews would be deployed through the weekend as weather allowed. They only call off efforts if it’s determined operations would be dangerous.

Nets will continue to be deployed through the next couple weeks. Burckhardt encourages fishermen to get in on the action, but asks them to avoid the nets if possible; each net costs the department more than $400.

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