Thanks to some dingbats who thought it would be a good idea to illegally plant walleye in Buffalo Bill Reservoir, Wyoming Game and Fish officials are looking at a long-term suppression effort to protect a popular wild trout fishery that ranks as one of the top in the state.
The reservoir was created in 1910 and is only 10 miles west of Cody, Wyoming, along the route to Yellowstone National Park’s East Entrance. Beginning in 1949, rainbow trout were stocked in Buffalo Bill, which captures runoff from the north and south forks of the Shoshone River. Lake trout and cutthroat were added in 1955, even though the rivers were already home to native cutthroat trout. In 1995, the Wyoming Game and Fish Department decided to halt all stocking in the reservoir. It is now the only self-sustaining wild trout reservoir in the state.
Then sometime in 2002 or 2003 someone decided to introduce walleye to the reservoir, likely from Deaver Reservoir northwest of Lovell, Wyoming. Scientists can tell this by examining the fish’s ear bone, or otolith.
Walleye are a predatory fish, and in Buffalo Bill Reservoir their main dining target became the plentiful mix of trout. It wasn’t until 2008 that walleye were first documented in the lake, so the fish had five to six years to grow and flourish. That’s important to note because a female walleye can produce up to 400,000 eggs a year. In comparison, a 13-inch female trout will produce only about 1,000 eggs.
Since 2008, WGFD biologists and technicians have been scrambling to try and understand how many walleye are in the lake (an estimated 15,000) and what will be the best way to control their growth (a combination of angling and gillnetting). Last spring, crews netted and electrofished walleye spawning areas and removed 800 fish in three weeks.
“It was refreshing to see we could keep that population suppressed with a lot less effort than I thought,” said Jason Burckhardt, a fisheries biologist for WGFD in Cody. “We’re pretty effective at capturing those fish by concentrating on removing them when they are spawning. It was also surprising to me the angler harvest of walleye, which is a key component to keeping that population suppressed.”
Fishing regulations on the reservoir require anglers to kill any walleye they catch.
This year, some walleye will be captured and fitted with radio telemetry devices to see if walleye are spawning anywhere that Burckhardt and his crew don’t know about. The spawning grounds discovered so far have been in less than 6 feet of water.
The calculations about how much continued gillnetting may cost Wyoming hasn’t yet been determined, Burckhardt said, which may involve hiring somebody to do the actual netting. “We’re working on that right now.”
Until a few weeks ago, WGFD wasn’t even sure the battle would be worthwhile. But now that the fight looks doable, the agency is moving forward with suppression efforts.
“I think we’re plowing new ground here,” Burckhardt said. “People have looked at suppression, but we’re the first to do it with walleye.”
People from around the state, country and world visit the Cody area to fish, often stopping on their way to or from Yellowstone National Park.
“The North Fork of the Shoshone and Buffalo Bill are some of the crown jewels of fishing in Park County,” Burckhardt said.
So taking care of those jewels to ensure they continue to thrive will be a main effort for WGFD until the walleye population winks out. How to achieve that final solution, though, is unknown. One idea being considered is the planting of male walleye that carry only two male chromosomes. With these males in the system, the chances for all-male hatches of walleye eggs increases. Through electrofishing, WGFD could even remove males to increase the chances the modified males would fertilize eggs. With fewer females there would be fewer egg layers and therefore fewer walleye.
It’s a method still in its infancy that’s being investigated on cutthroat trout waters in Idaho where invasive brook trout are a problem.
“It’s a pretty interesting concept to stock those fish to skew the sex ratio,” Burckhardt said. “It seems counter-intuitive, but it makes sense if you can wrap your head around it.
“But the jury is still out on how effective it might be and where it’s applicable,” he added.
In the end, all of the work to quantify, assess and begin removing walleye has added up to thousands of dollars of unnecessary expenses — fishery dollars that could have gone elsewhere — as well as the diversion of personnel that could be working somewhere else. As suppression costs continue to add up, the final price tag will be in the millions of dollars.
“While the effects of the walleye (on the fishery) have not been seen yet … it’s possible and likely there will be some effect in the not-too-distant future,” Burckhardt said.
Unfortunately, it comes at a time when the fishery is in its prime — growing fat, healthy trout.
“The overall size is much larger than it has been in the past.”