Wyoming biologists working to expand range of rare fish


CASPER, Wyo. (AP) – Tucked away in the remotest stretches of some of the remotest streams is a small fish that in the spring uses its head to build forts for its eggs.

The hornyhead chub, known for strange bumps that help in fort building, is one of Wyoming’s rarest fish. It’s also one of its most interesting, if you ask any local fisheries biologist.

The 5- to 7-inch long fish can carry rocks as big as its head to build a wall around its nest. It also allows other small, native fish to lay their eggs in its fort, then protects the array of soon-to-be fry.

And the hornyhead chub is making a bit of a comeback.

With some help from Wyoming Game and Fish Department biologists, it recently expanded its range by 50%. For a fish that was only in two streams, a 50% increase is notable.

“One of our goals, and mine personally, is that we don’t lose a single native species in this state, whether a fish or amphibian or bird,” David Zafft, fisheries management coordinator for Game and Fish, told the Casper Star-Tribune. “We won’t hang onto them everywhere, but some places we can. There are so few areas where the hornyhead chub lives, and we can’t afford to lose it.”

Ask an angler in, say, Ohio, and they’ll likely wonder why the fuss about a fish so common it’s used as bait. The hornyhead chub’s native range extends from eastern North Dakota to western New York and down to northern Arkansas. In much of that area they’re plentiful. But many western streams, where few populations remained as glacial relics, it has struggled.

It no longer exists in Colorado and Nebraska, and in Wyoming, where it never had much of a native range, it lived in isolated portions of the Laramie and north Laramie Rivers.

Causes for extirpation from states like Colorado likely run the gambit from degraded habitat and introduced predatory fish like smallmouth bass to increased levels hormones in the water that cause males to be unable to spawn, said Zafft.

In Wyoming, the fish lived in about 16 miles of the Laramie River and eight miles of the North Laramie River in the Laramie Range.

That was until the Arapaho Fire.

The 2012 blaze was one of Wyoming’s largest at the time, burning about 100,000 acres and destroying 90 buildings. A large rain shortly after sent a flood of ash, soot and debris down the winding, North Laramie River so thick that it eliminated all eight miles of habitat and killed thousands of fish, including the hornyhead chub.

“If they don’t have a place to move to get out of the way, suspended ash coats their gills and suffocates them,” said Steve Gale, fisheries biologist in the Laramie region.

So Game and Fish biologists worked with landowners along the North Laramie River and began transplanting hornyhead chub from the Laramie River. Each year proved more promising, and this year, populations in the North Laramie matched those from before the fire.

But even with those successes, the chub still had a very limited range in Wyoming.

Some might ask why it matters if a small fish with funny horns on its head lives or dies. It’s not a sport fish. It’s not even a bait fish. It is, however, a critical part of Wyoming’s natural systems, said Zafft.

“I consider them more of an indicator species of healthy habitat like somebody might the spotted owl in a northwest boreal forest,” Zafft said.

The chub requires cold, clean water and plenty of gravel to build its nests.

“If you have hornyhead chub around it means you have bears and birds and all sorts of native species because they have a pretty unique set of habitat requirements that are very easy to mess up,” he added.

And about that nest building.

During breeding season, the males grow a dozen or more small bumps – tiny horns, if you will – on the top of their heads. They use those to scoop and scoot rocks and dirt into a pile. The male then picks up rocks with its mouth and drops them on top, increasing the mound.

About five years ago, Game and Fish partnered with the University of Wyoming’s cooperative fish and wildlife unit to look at other areas the hornyhead chub may have lived, and could successfully be reintroduced in Wyoming.

Biologists found one historical record of the hornyhead chub in the Sweetwater River. That lone fish was collected in 1852 and is currently preserved in the Smithsonian, said Paul Gerrity, a fisheries biologist in the Lander region.

No one knows why other records don’t exist from the Sweetwater, but Gerrity has a few theories. Historical records from the 1800s talk about how cattle moving through on the Oregon Trail overgrazed a mile or more on the sides of the Sweetwater River. Because the hornyhead chub exists in such isolated portions of streams, it’s entirely possible that livestock grazing wiped the small population out with that lone specimen proving their existence.

The study also labeled the Sweetwater River as prime hornyhead chub habitat because of its clear water, gravel bottom, lack of the most concerning nonnative predators and the existence of other native fish like Iowa darter and bigmouth shiner.

So in September, Game and Fish biologists released 308 hornyhead chub collected from the Laramie River into the Sweetwater. Another transplant is planned for 2021.

“We have a moral obligation, and Game and Fish has a statutory obligation, to ensure their existence,” Gerrity said.

Plus, he added: “They’re just a neat native fish.”

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