Small Fish, Big Rivers
When you think of big water you often think of big fish. Along Wyoming’s North Platte and Bighorn rivers, images of large trout, and even walleye or sauger, often come to mind.
But what about the little fish, many of which are native species? Not a lot is known on a broad scale about which small-bodied fish live in these two rivers or where they’re located. However, recent work by the Wyoming Game and Fish Department on the North Platte River shed some answers, which will lead to a similar project on the Bighorn River this spring.

“We’re responsible not only for managing sport fisheries and providing angling opportunities, but also to manage and maintain all the native species we have in our rivers and streams,” said Stephen Siddons, Game and Fish fisheries biologist in Laramie who worked on the North Platte River project.

Electrofishing was a common technique used to sample small fish in the North Platte River. (Photo by Travis Neebling)

“It’s hard to do any management work or understand what’s happening with those species without spending time looking for them and getting an idea of where they live and how many there are. The information we gather can give us ideas to expand some of these native species’ distributions by restoring them to areas where they were lost to before. The idea is to give them more habitat to live in and persist longer.

“And, all of those big fish need something to eat, too. A healthy aquatic environment and ecosystem provides food for fish to grow larger, and those small-bodied fish can be food for them.”

North Platte details
The project started in 2017, and sampling wrapped up in 2020. It started on the upper part of the river above Seminoe Reservoir, which Travis Neebling, Game and Fish fisheries biologist in Casper, said is the unregulated portion of the river with no dams and natural stream flow. From 2018-20 samples were taken on the lower North Platte where there are more dams and water flows vary.

“We basically sampled from just below the Colorado border all the way down to where it flows into Nebraska,” Neebling said. “Not every inch of it. We were limited where we could get access in some areas.”

The North Platte River begins at an elevation of 7,740 feet, and drops to 4,025 feet when it leaves Wyoming. Seven major dams exist along the main river channel, which creates five reservoir complexes. Over the years dams have altered water flow and temperature. There also are smaller dams along the river for irrigation diversions, most of which are downstream from Casper, along with a dam that provides cooling water for the coal-fired Dave Johnston Power Plant near Glenrock.

Electrofishing is a common technique when sampling any body of water for fish, and this was used in certain areas of the North Platte.

A relatively new technique for rivers in Wyoming was used in this work, too.

Trawling is commonly used to sample small-bodied fish in rivers in the Midwest, and Neebling said he used this technique during his master’s degree work in Iowa. There are several different kinds of trawls, but the ones used on the North Platte were pulled behind a boat and were dual-layered where the inside featured a large-mesh net designed to catch larger fish and debris and allow small fish to move through where they were caught in a smaller mesh net.

Screenshot-2023-01-06-at-10-00-47-AM.pngWyoming Game and Fish Department workers look for small fish in a trawl during sampling along the North Platte River. Trawling is a common technique to sample small fish in large rivers. (Photo by Travis Neebling)

“It was very effective for those fish species found in the main channel of the river,” Neebling said. “It can be used on side channels and backwaters, but it picks up a lot of debris. More traditional gears work better in those areas.”

Fish findings
A total of 22,337 fish of 33 species were collected from 213 backpack electrofishing attempts. There were 328 trawl hauls that produced 5,827 fish from 24 species. Electrofishing from rafts was also conducted, but not in shallow water. There was sampling in some reservoirs, such as Alcova, Pathfinder and Seminoe. Fyke nets were used in those waters. Fyke nets combine netting bags mounted on supports and anchored to the bottom with a trap fixed at the end.

Screenshot-2023-01-06-at-10-03-52-AM.pngThe orangethroat darter was not found in the North Platte River in Wyoming in the past, but recent work found this small fish to be fairly widespread. (Photo by Travis Neebling)

There were six species of small-bodied fish sampled that are Species of Greatest Conservation Need in Wyoming. That designation means those species’ conservation status warrants increased management attention, funding and consideration in conservation, land use and development planning in the state. Those species include: bigmouth shiner, brassy minnow, common shiner, Iowa darter, northern plains killifish and orangethroat darter.

Screenshot-2023-01-06-at-10-05-57-AM.pngThere were only isolated populations of Johnny darters in the North Platte River in Wyoming 50-60 years ago, but they are now more abundant in the river system. (Photo by Travis Neebling)

Siddons said some species were doing better than originally thought. Orangethroat darter was a fish not previously found in the North Platte in Wyoming and was found to be fairly widespread. Iowa darters and brassy minnows were found in good numbers in the lower part of the river. Bigmouth shiners seem to be doing better lower in the river than anticipated, but they were absent from the upper stretches.

“The most important findings were the Species of Greatest Conservation Need, but also to collect data on nonnative species all the way up to the more common species,” Siddons said. “We got a good snapshot of all the species that were collected. It's the only holistic baseline data we have for the North Platte in Wyoming.”

Neebling said none of the species thought to be extirpated for a number of decades were found. He also said some native species like Johnny Darter that had isolated distributions 50-60 years ago are now widespread in the river.

The news wasn’t all good. Neebling said one aquatic invasive species — brook stickleback — was found to be more widespread in the river than originally thought.

Upcoming project
In March, Game and Fish will begin work on a similar project on the Bighorn River to survey for native sturgeon chub and other nongame species within the mainstream of the river. It will encompass about 137 river miles, starting at the Wedding of the Waters where the Wind River becomes the Bighorn River and ending at the mouth of Bighorn Lake. 

The project is scheduled to be completed in February 2025.

The Wyoming Game and Fish Department will sample for small-bodied fish on the Bighorn River starting in March. The project will be completed in February 2025. (Photo by Joe Skorupski)

Beth Bear, Game and Fish aquatic assessment crew supervisor and lead on the project, said similar work on the Bighorn River was done around 2006-07, but it mostly looked at tributaries. Joe Skorupski, Game and Fish fisheries biologist in Cody, said a project was completed in 2017-18 on the Bighorn River that focused on critical habitat areas where nongame, small-bodied fish species were prevalent — specifically, the lower Bighorn River and lower Nowood River. That study was an effort to establish long-term monitoring of the nongame, small-bodied fish in the Bighorn River. During the project, sturgeon chub were captured which were not observed since 2002 and thought to be extirpated from the Bighorn River.  The finding spurred multiple projects, one being the upcoming project starting in March.

The sturgeon chub was petitioned for listing under the Endangered Species Act in 2016. A positive 90-day finding was made in December 2017. The U.S Fish and Wildlife Service and at least 13 state agencies are now engaged in the development of a species status assessment of sturgeon chub. Although data from this project will likely be collected too late to inform the species status assessment which will be released in September 2023, knowledge of the species status in the Bighorn River will be valuable if the U.S. Fish and Wildlife Service determines listing the sturgeon chub under the ESA is warranted.

“If we can get more and better information for our sensitive species we have in the state it could preclude listing. That’s a really good thing for resources for the species, and state and federal resources,” Skorupski said.

The work on the North Platte River provided insight into effective techniques to sample some of these small-bodied fish in large rivers.

“That keyed us into the fact that perhaps because of water flows and sampling gear in the past we just hadn’t been sampling species that were there,” Bear said. “This work on the Bighorn River will use similar methodology and some things we learned from the North Platte River project and apply it to the Bighorn River.”

Sturgeon chub is not the only species of importance with this project. Bear said plains minnow and western silvery minnow are two others involved in the surveys, which are native to Wyoming. Game and Fish data on these two species are outdated, and it is unknown if one or both still exist in the river. 

“We don’t really have a complete picture of where those species are, especially in the Bighorn River system,” Bear said.

Good things in small packages
Why such an effort for small fish? Many people are more concerned about fish they can catch and eat such as trout, walleye, sauger and catfish.

“These small-bodied fish are part of the ecosystem,” Bear said. “We tend to find when we lose a species it can have impacts on the entire ecosystem. These species are native to Wyoming. They’ve been in Wyoming for a long time and they’re important to the balance and the ecosystem to places like the Bighorn River. 

“They have intrinsic value as well. They’re really fascinating. They’re very persistent in a lot of areas. They survive in places we wouldn’t expect them. It also is to get a baseline so we can look at changes that might be happening — environmental changes, wildfire, increased water temperatures. Without a good baseline on some of these native, small-bodied fish it’s really hard to detect change over time and it will be hard to detect change from other invasive species as well.”

Bear also said the work could provide insights into the impact the invasive brook stickleback has on other small-bodied fish in the Bighorn River.

“It’s about knowing what we have, how the species are distributed and when that occurs,” Skorupski said. “From there we can identify other projects specific to that species once we know where and when they are there.”

Robert Gagliardi is the associate editor of Wyoming Wildlife.
Photographer Info
Travis Neebling

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