Distribution and movement of humpback chub in the Colorado River, Grand Canyon, based on recaptures

Mark-recapture data from the federally endangered humpback chub Gila cypha in the Colorado River, Grand Canyon, were analyzed from 1989 to 2002 to determine large-scale movement patterns and distribution. A total of 14,674 recaptures from 7,127 unique fish were documented; 87% of the recaptures occurred in the same main-stem river reach or tributary as the original captures, suggesting restricted distribution by most fish. A total of 99% of all recaptures were from in and around the Little Colorado River (LCR), a tributary of the Colorado River and primary aggregation and spawning location of humpback chub in Grand Canyon. Time at liberty averaged 394 d, but some fish were recaptured near their main-stem capture location over 10 years later. Proportionally fewer large (>300-mm) humpback chub exhibited restricted distribution than small (