Habitat Selection and Movement of Adult Humpback Chub in the Colorado River in Grand Canyon, Arizona, during an Experimental Steady Flow Release

Abstract

AbstractEffective conservation and restoration programs for many native riverine fish communities are highly dependent on regulated river operations developed by water managers. Successfully implementing river flows to meet human needs and minimize ecosystem impacts requires understanding the linkages between hydrology, physical habitat, and fish ecology. In the Colorado River within Grand Canyon, Arizona, altered river conditions following the construction of Glen Canyon Dam have contributed to the decline of Humpback Chub Gila cypha. In 2010, a management experiment was implemented to contrast the modified low fluctuating flow policy with an experimental steady flow release. We assessed habitat selection and movement of 30 adult Humpback Chub implanted with acoustic telemetry tags during 2 months of fluctuating flow followed by 2 months of steady flow. We found that telemetered Humpback Chub used eddies extensively while avoiding runs and were associated with intermediate depths and larger substrates. During both flow treatments, Humpback Chub exhibited small daily movements of about 100 m/d. No effect of the flow experiment was observed on Humpback Chub habitat selection or movement. However, nearshore habitat use by Humpback Chub increased with turbidity fluxes caused by tributary floods. Overall our results suggest that adult Humpback Chub habitat selection and movement may not be impacted by the current hydropower operations, but habitat use and spatial distribution are influenced by changes in turbidity which has changed greatly in the Colorado River since the completion of Glen Canyon Dam.Received February 1, 2013; accepted August 28, 2013Published online January 17, 2014