Razorback Sucker research and monitoring in Lake Mead, Nevada and Arizona.

Authors: Harrison* Mohn, Brandon Albrecht, Ronald Rogers, Ron Kegerries

Year: 2015 (xlvii)

Abstract

The natural recruitment, movement patterns, and habitat use of adult Razorback Sucker Xyrauchen texanus in Lake Mead have been studied in some capacity for the last 20 years. As past studies have shown, Lake Mead is somewhat unique in terms of consistent and continued recruitment of wild Razorback Sucker and the presence of juvenile individuals. Several methodologies were employed in long-term monitoring during the 2014-2015 field season to assess reproductive activity and population demography including; sonic telemetry, trammel netting, nonlethal aging, and larval fish surveys. The collection of these data aided in the identification of primary spawning areas, documentation of successful reproduction, and continued recruitment with a number of new, wild Razorback Suckers captured in Las Vegas Bay, Echo Bay, and the Muddy River/Virgin River inflow area. Additionally, efforts to specifically target juvenile Razorback Sucker in Lake Mead utilizing sonic-tagged juvenile individuals, were employed to better understand why Lake Mead Razorback Suckers are able to demonstrate natural recruitment. Movement and contact locations of sonic-tagged juvenile Razorback Suckers were used to help to characterize the associated habitat by quantifying the physicochemical attributes (temperature, dissolved oxygen concentration, conductivity, pH, turbidity, depth) and the qualitative assessment (type and percent composition) of inundated cover and substrate. Furthermore, a number of methods were also used to describe the associated fish community in these preferred areas. Continued research concentrating on understanding naturally occurring recruitment of Razorback Sucker in Lake Mead, will aid in assembling conservation applications for the species throughout the Colorado River basin.