Parasitism and Body Condition in Humpback Chub from the Colorado and Little Colorado Rivers, Grand Canyon, Arizona

Glen Canyon Dam has greatly altered the Colorado River in Grand Canyon. The Little Colorado River (LCR) provides a small refuge of seasonally warm and turbid water that is thought to be more suitable than the Colorado River for endangered humpback chub Gila cypha. However, the LCR has low productivity and contains nonnative fishes and parasites, which pose a threat to humpback chub. The Colorado River hosts a different suite of nonnative fishes and is cold and clear but more productive. We compared condition factor (K), abdominal fat index (AFI), and presence and number of two introduced pathogenic parasites (Lernaea cyprinacea and Bothriocephalus acheilognathi) between juvenile (