Adult and juvenile razorback sucker (Xyrauchen texanus) research and monitoring on Lake Mead, Nevada and Arizona

Authors: Ronald Rogers, Brandon Albrecht, Ronald B. Kegerries, Zachary Shattuck

Year: 2012 (xliv)

Abstract

The recruitment, movement patterns, habitat use, and population trends of razorback sucker (Xyrauchen texanus) in Lake Mead, Nevada and Arizona were researched and monitored with funding provided by the Lower Colorado River Multispecies Conservation Program in 2012. In order to assess this unique, wild razorback sucker population, several methodologies were employed during the razorback sucker spawning season in 2012 including: sonic surveillance, trammel netting, nonlethal aging, and larval fish surveys. As evident from the data, Lake Mead razorback sucker demonstrated successful spawning in 2012. A total of 85 adults and 1 juvenile, wild and stocked aggregate razorback sucker were captured from four research/monitoring sites throughout the lake providing additional data to help document natural recruitment. Forty-nine new razorback sucker fin rays were collected for laboratory aging analysis and help to clarify recruitment patterns. To date, 710 unique individuals have been identified in Lake Mead, and a total of 395 fin ray sections have been collected and analyzed, helping to illustrate the continued recruitment of wild razorback sucker from 1978 through 2008. Aging data demonstrate that the 2005 year-class continues to be a strong year for natural recruitment in Lake Mead, and similar lake conditions in 2011 provides optimism that we will continue to find young, wild cohorts as they become susceptible to sampling gear during future monitoring efforts. Furthermore, adult movement patterns demonstrate that Lake Mead razorback sucker continue to utilize several areas of the lake during the spawning season. Observations of sonic fish movements from the Colorado River inflow area into the lower Grand Canyon lend further insight into the role that the river proper may play for this unique razorback sucker population. A pilot study was initiated in 2012 to focus on juvenile razorback sucker which should help to provide information regarding why Lake Mead razorback sucker are able to demonstrate natural recruitment. Continued research concentrating on this rare life stage should aid in the understanding of recruitment in Lake Mead. Research on Lake Mead may also have application elsewhere in the basin for the benefit and conservation of the species.