Great Basin Naturalist


We evaluated distribution, habitat use, spawning, and species associations of the endangered humpback chub (Gila cypha) in the Yampa and Green rivers, Dinosaur National Monument, from 1986 to 1989. Adult and juvenile humpback chub were captured in high-gradient reaches of Yampa and Whirlpool canyons where they were rare (n = 133, < 1% of all fish captured). The fish was primarily captured in eddy habitats in association with 7 native and 12 nonnative fish species. Roundtail chub (G. robusta) were widely distributed in eddies, pools, runs, and riffles. Humpback chub (n = 39) and roundtail chub (n = 242) in reproductive condition were sympatric in eddy habitats during the 5–6-week period following highest spring runoff. River temperatures at this time averaged about 20 C. Nonnative channel catfish (Ictalurus punctatus) were abundant in eddies yielding humpback and roundtail chubs, suggesting a potential for negative interactions between the native and introduced fishes.