Use of Existing and Reconnected Backwater Habitats by Hatchery-Reared Adult Razorback Suckers: A Predictive Model for the Imperial Division, Lower Colorado River

Abstract

Information regarding the life history and biological requirements and preferences for the razorback sucker Xyrauchen texanus is limited. Current recovery efforts involve rearing fish to juvenile or adult stages in hatcheries before they are released into areas of critical habitat that increase their survival. Our objectives were to develop a model based on habitat use by hatchery-reared razorback suckers in the lower Colorado River of Arizona and California for predicting preferred habitat and to determine whether fish would use reconnected off-channel habitats. To this end, we monitored the use of existing and reconnected habitats by hatchery-reared razorback suckers implanted with sonic transmitters. Off-channel (backwater) habitats were preferred over main-channel or side-channel habitats. We constructed a model using logistic regression to predict which types of backwaters (based on morphology and water quality) were most suitable for use by razorback suckers. The model works well for predicting sites that are less suited for use and can be used to prioritize habitats for reconnection purposes because razorback suckers were found to utilize reconnected habitats.