Distributions, abundances, and movements of small, nongame fishes in a large Great Plains river network
Duncan, Michael Bennett
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The Yellowstone River is the longest unimpounded river in the conterminous United States and was thought to support a diverse fish assemblage; however, comprehensive data on the small nongame fish assemblage was lacking. I evaluated the sampling methods often used to capture small-bodied fishes in the channel margins of large Great Plains rivers, determined the distributions and abundances of these fishes in the Yellowstone River, characterized the movements of selected native cyprinids between the Yellowstone River and its tributaries, and assessed assemblage differences between the Yellowstone and Missouri rivers. Catch-per-unit-effort, species richness, and ranges of total lengths were greater in fyke net catches than in seine catches. Forty-two species (24 native and 18 nonnative) were captured in fyke nets in the lower Yellowstone River. Emerald Shiners Notropis atherinoides, Western Silvery Minnows Hybognathus argyritis, Flathead Chubs Platygobio gracilis, Sand Shiners Notropis stramineus, and Longnose Dace Rhinichthys cataractae composed nearly 94% of fyke net catch. Sturgeon Chubs Macrhybopsis gelida, Channel Catfish Ictalurus punctatus, Flathead Chubs, Stonecats Noturus flavus, and Sicklefin Chubs Macrhybopsis meeki composed 89% of the otter trawl catch. Sicklefin Chubs were captured as far as 18 river kilometers upstream of Glendive, Montana; Sturgeon Chubs were captured as far upstream as the Tongue River confluence. Otolith microchemistry analysis revealed that 69% of Western Silvery Minnows, 65% of Flathead Chubs, and 42% of Sand Shiners moved between main-stem and tributary habitats. The timing, frequencies, and patterns of movements varied among species. In my comparison of the Yellowstone and Missouri river fish assemblages, native and nonnative species richness were highest in Yellowstone River fyke net catches but proliferation of nonnative species was low. Total CPUE was highest in the Yellowstone River (median = 152 fish/net night), intermediate in the Missouri River below the Yellowstone River confluence (44 fish/net night), and lowest in the Missouri River above the confluence (21 fish/net night). Collectively, these studies provide a better understanding of the biotic and abiotic factors that help influence the distributions, abundances, and diversity of life-history strategies of small, nongame fish in Great Plains rivers.