The consequences of releasing fish tank pets into West Newton Lake will significantly change fishing for about a decade at both the "put-and-take" lake as well as East Newton, a popular catch-and-release trophy trout fishery. Illegally introduced goldfish have plagued the lakes for the past few years and have now reduced a working group to take drastic action to return the fisheries to their former glory.

Goldfish were dumped in West Newton Lake, allegedly by pet fish aficionados, prior to 2020. Then, during high water events, the fish invaded East Newton and have taken over the prime trophy trout fishing habitat.

"It's a carpet of goldfish, a school of them ... just sort of swimming around in this big orange blob," said frequent East Newton fly fisherman Dan Cossaboon, about conditions at the lake.

He has watched the invasive fish population grow quickly at the lake, robbing the treasured trout of needed resources. The fishing in East Newton is still productive, but, according to the East Yellowstone Chapter of Trout Unlimited, "all is not well at the lakes."

"Newton Lakes are near and dear to the hearts of Cody residents as well as for visitors from near and far. In addition to popular fishing lakes, paddle-boarders, kayakers, mountain bikers and hikers enjoy the natural setting with the Absaroka Range serving as a backdrop," the nongovernmental organization said in a recent press release.

West Newton Lake has long served as a popular cutthroat trout fishery. However, over 75% of the fish biomass in the lake now consists of goldfish, suckers and chub. The productivity for the cutthroat trout has declined significantly due to competition from these illegally introduced species.

"I can't say with the straight face that the trout and West Newton lake right now offer quality fishing opportunities," said Game and Fish Cody Region Fisheries Supervisor Sam Hochhalter.

The Wyoming Game and Fish Department's Speas Hatchery will deploy tiger musky (a sterile hybrid of northern pike and muskellunge, or muskie) starting in September. The aggressive fish, which can grow to more than 40 inches in length at maturity, are expected to devour invasive goldfish, white suckers and lake chub before diminishing enough to repopulate the lake with Yellowstone cutthroat trout. The average life expectancy of the tiger muskie is 8 years, providing a unique fishing opportunity for those wanting to tangle with the aggressive, toothy fish, Hochhalter said.

"[Tiger musky] go in pretty small — 8 or 9 inches long — and it takes them a couple years before they get big enough to start aggressively preying on goldfish and white suckers as well as lake chub," Hochhalter said. "Certainly, from a fisherman standpoint, in a couple years it's going to be a big change in what opportunities are present in West Newton, because we will no longer stock trout in there. The hope is, I'm confident we can grow 30- to 40-inch tiger muskie, and with that size and with a fairly modest abundance, they will have a huge impact on goldfish and white suckers."

Hochhalter said tiger musky will grow to about 24 inches within a couple years and then begin to make a huge dent in the invasive populations. The trout population has essentially crashed, with the cutthroat trout fishing producing smaller than average trout in poor condition, he said.

"We've seen here in the last three to five years, a very pronounced reduction in the size structure and the body condition of the stocked trout," he said. "That's a consequence of a lot of the lakes' productivity going into growing goldfish and suckers, as opposed to trout."

The department will not be stocking trout in the lake when tiger musky abundance is high. So, it's probably going to be on a "seven-to-10-year cycle," Hochhalter said.

"It's a big shift in fishing opportunities in West Newton, but it makes the most sense, given the cost of rotenone and the logistics behind it," he said. "East Lake is kind of a different story."

East Newton Lake angling is now also at risk due to the goldfish, but still has a large population of beautiful trout, including rainbow and cutthroat trout. The lake still fishes well but productivity will decline as the goldfish population expands and will eventually require a two-year chemical treatment to remove all fish from the lake at the cost of about $150,000. The department will wait until angling diminishes before doing the chemical treatment.

Newton Lakes Workgroup

Issues at the two lakes aren't just affecting anglers. Recreation at the lakes also helps drive the local economy, Hochhalter said.

"The vast majority of people that choose to live in the communities around Wyoming, Cody being one, is for the outdoor resources that are at your fingertips," he said.

The anticipated decade it will take to rejuvenate both lakes may seem long, but it's all relative.

"In terms of fish management, it is a short term solution," he said of the deployment of tiger muskie. "Most of the decisions we make fishermen don't see the outcome of those decisions for many years. So to think that fishermen could be catching a 24-plus-inch tiger muskie in two years, that's about as short term as it gets."

Responding to issues at the beloved lakes adjacent to the new Outlaw Trails mountain bike course, Wyoming Game and Fish, East Yellowstone Trout Unlimited, and the Cody Anglers Group initiated the Newton Lakes Workgroup (NLWG) in 2020 to address management issues for the lakes. The group has been working well together, Hochhalter said, and made the decision to try the tiger muskie option rather than spending a total of $300,000 to use rotenone (a short-lived chemical often employed by fisheries biologists to remove unwanted fish from lakes and streams) to empty both lakes of all fish and then start again from scratch.

"We looked at rotenone just to kill all the aquatic life in the lakes and then restock it. It's expensive. It takes two years and we don't want to do it unless we have to. So we're going to try a different approach," said East Yellowstone Chapter of Trout Unlimited President Larry Timchak.

Both these lakes are prime examples of the economic and ecological consequences of illegal fish introduction, he said.

"Please think twice when you no longer want your goldfish. Releasing them in our local fisheries comes at a high cost. And it may come at a high cost personally because illegal fish stocking is considered a high misdemeanor in Wyoming and can result in fines up to $10,000," Timchak said.

Individuals found guilty may face up to one year in jail and may face a lifetime revocation of Wyoming hunting and fishing privileges. And individuals may be required to pay restitution for damages caused by the illegal stocking. 

Bucket biologists

Illegal bucket biologists have already cost the state dearly. Illegal fish introductions usually come from illegal minnows used as bait, or by anglers deliberately putting the fish there for future opportunity, said Game and Fish Senior Multimedia Specialist Ray Hageman.

"Game and Fish will only introduce new species into waters after thoroughly researching the suitability of the fish for that water and assessing risks to nearby waters," he said in March.

Brook stickleback, illegally introduced as baitfish in the North Platte and Bighorn rivers, feed heavily on aquatic invertebrates, midges and scuds important to trout. Possession of live brook stickleback is illegal in Wyoming. Yet, there are several species of concern, even if anglers want desirable catches in a nearby fishery.

"Walleye are great game fish, but, they feed heavily on other fish. A water suited for walleye must produce a good supply of forage for it. If good forage is lacking, other game species get picked on," Hageman said.

Wyoming waters where walleye have been illegally introduced include Buffalo Bill Reservoir outside of Cody, and Lake DeSmet near Sheridan.

Illegally introduced burbot are now firmly established in Fontenelle and Flaming Gorge reservoirs, impacting popular Kokanee salmon and smallmouth bass populations and an illegal introduction of yellow perch into Saratoga Lake in 2022 resulted in Game and Fish removing all fish from the water, and restocking — "an expensive fix," he said.

Illegal stocking can also spread disease to other waters. No fish can be stocked in Wyoming without authorization by Game and Fish. Any fish not released immediately to the water or placed on a stringer, or in a container or live well is considered in possession of the angler, and must be killed before leaving the water of that fish’s origin.

Hochhalter said the NLWG, which started in 2020, has been a very positive experience.

"I get a ton of value out of with the ... group. It's not just me in a red shirt talking about a change in management. None of these decisions that we're talking about here today, nor really the movement of the outhouse development of the parking lot. When government agencies do that in isolation, it's a lot harder — more difficult. So what I really appreciate about the working group is they're all very passionate fishermen, first and foremost, and general recreationists. To get us all in one room and to brainstorm and talk about options that are available and come to an agreement on what makes sense based on everyone's interest in these lakes, is really, really valuable. This was vetted by some of the most passionate, best anglers in the Cody area."

If you have information about illegal fish stocking, contact the Wyoming Game and Fish Department's Stop Poaching Hotline at 1-877-WGFD-TIP (1-877-943-3847).