An assessment of long-term monitoring efforts for razorback sucker in Lake Mohave, Arizona and Nevada.

Authors: Brian R. Kesner, Abraham P. Karam, Carol A. Pacey, Paul C. Marsh

Year: 2009 (xli)

Abstract

The razorback sucker Xyrauchen texanus population in Lake Mohave has been monitored for more than 30 years, and augmented by stocking for nearly 20. During this time the population has declined from more than 100,000 individuals to fewer than 2,000. A lack of recruitment has resulted in a near complete loss of the wild population, while augmentation stockings have been decimated by striped bass predation. Sonic telemetry, multi-site mark-recapture analysis, and frequency analysis of mark-recapture data were used to verify results and assess bias. Six month post-stocking survivorship of razorback sucker assessed from sonic telemetry was highly variable, ranging from 6.8 to 66.7% for fish 38 cm total length (TL) and from 36 to 80% for fish 50 cm TL and larger, but within estimates from previous mark-recapture analyses. A multi-site mark-recapture analysis of “at large “ repatriated razorback sucker found significant short-term site fidelity indicating non-random assortment within Lake Mohave. However, survival estimates from the multi-site model did not significantly differ from estimates from single site models previously reported and ranged from 70 to 92% among sites. In addition, capture frequencies were not negatively correlated with the number of previous captures, indicating that handling did not impact survivorship. Thus, routine monitoring efforts as currently implemented provide accurate estimates of population abundance and survival for razorback sucker in Lake Mohave without significantly impacting their health, but precision is low due to highly variable size specific post-stocking survivorship.