Underwater survey methods to identify areas used by Razorback Sucker, Xyrauchen texanus, below Hoover Dam to Willow Beach, Arizona

Authors: Andrea Montony, Caireen Ulepic

Year: 2010 (xlii)

Abstract

Lake Mohave represents one of the last remaining wild populations of razorback sucker, Xyrauchen texanus, in the lower Colorado River. Razorback sucker monitoring extends from Willow Beach south to Davis Dam through annual round-ups, and larval collections. However, Hoover Dam to Willow Beach creates a problematic sampling area. Razorback suckers are visually identified by boat and helicopter and contacted through electrofishing yet these observations are limited by location and are depth dependent. The Lower Colorado River Multi-Species Conservation Program (LCR MSCP) Fisheries Group requested the assistance of the Lower Colorado Regional Dive Team to conduct underwater surveys identifying new areas used by razorback suckers. The survey area extended from below Hoover Dam to Willow Beach Arizona, encompassing approximately 14 river miles at depths ranging 6 to 60 feet. Methods were developed, where divers using SCUBA (self contained breathing apparatus) drifted downstream with the current recording depth, substrate, and time razorback sucker were observed. Survey data was used to create a map of the observed location’s of razorback sucker. Over a hundred razorback suckers were observed during the surveys, with the majority of observations occurring within two river miles below Hoover Dam.