Local extirpations of the federally endangered Topeka Shiner (Notropis topeka) have been linked to the introduction of Largemouth Bass (Micropterus salmoides). However, because other native minnow species have persisted at these locations, our objective was to test whether Topeka Shiners were more susceptible to predation by Largemouth Bass than other native minnows. We conducted behavioral observations of Topeka Shiners, Red Shiners (Cyprinella lutrensis), Bluntnose Minnows (Pimephales notatus), and Common Shiners (Luxilus cornutus) in an indoor experimental stream, in which we examined the interactive effects of cover and the presence of a predator on longitudinal and lateral position, height in water column, cover use, and activity of these minnows. Significant differences in habitat use and response to bass were observed among species, but there was no evidence to suggest that Topeka Shiners would be more susceptible to predation than other native species. Subsequent experiments in outdoor experimental streams that allowed Largemouth Bass to forage on an assemblage of these four minnows indicated that consumption rates across species were similar, further suggesting that Topeka Shiners were not more susceptible to predation than the other minnows. Although our experiments suggest that Largemouth Bass randomly prey on this guild of minnows, the added mortality and potential indirect effects of this introduced predator likely have negative effects by further reducing the abundance of already rare Topeka Shiners.

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