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Sturgeon chub

Macrhybopsis gelida . By Niall Clancy

This story is featured in Montana Outdoors July-August 2019 issue.

A few summers ago while working as a Montana Fish, Wildlife & Parks fisheries technician, I accompanied a biologist up the Powder River, a tributary of the Yellowstone River in southeastern Montana not far from Miles City. We were using radio telemetry to locate a pallid sturgeon tagged by FWP several years earlier.

Though we didn’t locate the sturgeon, the trip was notable because it was the first time I had seen so much of the Powder River. True to its name, the Powder is naturally laden with fine sediment—a smooth chocolate ribbon running through the prairie. It’s also a major stronghold of one of Montana’s least-known fish, the sturgeon chub.

Identification
Although named for its fleeting resemblance to the much larger members of the sturgeon family, the sturgeon chub is actually a member of the minnow family. A relative of daces and shiners, it can be distinguished from these and other small forage fishes by its slender body and long snout, which overhangs its horizontal mouth. Averaging two to three inches long, the species can be differentiated from the similar looking longnose dace by its noticeably lighter coloration and tiny barbels at both corners of its mouth.

Sturgeon chubs are bottom dwellers, typically found in shallow areas of large, slow-flowing rivers. Unlike the sicklefin chub, another closely related species, the sturgeon chub prefers areas with exposed gravel and swift current—a type of habitat uncommon in sluggish, muddy streams and rivers.

Feeding
Finding prey in the murky waters of the Powder River is difficult for many fish species, especially sight feeders like smallmouth bass. But the sturgeon chub is well adapted to life in limited visibility. The fish’s entire underbelly is covered in small sense organs. It uses these to “taste” the stream bottom, picking out small aquatic insects such as midge larvae. Biologists consider the sturgeon chub one of the best “tasters” in the animal kingdom.

Distribution and Conservation Status
Due to their small size and scarcity, sturgeon chubs are difficult to capture. Little is known about the species’ movement or spawning behavior.

What biologists do know is that the sturgeon chub’s historic range included 13 states from Montana and North Dakota south to Arkansas and Tennessee. In Montana, it was found in the main stems and larger tributaries of the state’s Missouri and Yellowstone Rivers. “The first Montana specimens were taken by the Railroad Survey (1853-1855) somewhere in the Milk River,” writes C. J. D. Brown in Fishes of Montana.

The statewide range has since shrunk by 50 percent due to river alterations from dams, channelization (straightening stretches and removing pools and spawning gravel), and other development that degrades or eliminates habitat. In Montana today, sturgeon chubs are found primarily in the main stems of the Missouri, Yellowstone, and Powder Rivers.

Though conservationists petitioned for its listing under the Endangered Species Act, further study determined that the sturgeon chub was not at significant risk of extinction. Still, due to extensive habitat loss, Montana and nine other states consider the sturgeon chub a “species of special concern.” Because predicted lower stream flows from climate change will likely make life harder for the sturgeon chub, FWP biologists are monitoring populations to gather information that will help conserve this unique prairie fish. Bear bullet

Niall Clancy is a writer in Hamilton. Illustration by Joseph Tomelleri.

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