Preliminary results of using stereo-video technology as a means of noninvasively measuring fish length to monitor population dynamics of the critically endangered Devils Hole pupfish, Cyprinodon diabolis

Authors: Bailey Gaines, Kevin P. Wilson, Michael R. Bower

Year: 2010 (xlii)

Abstract

The use of length frequency population samples has long been used by fisheries managers as a staple tool to monitor population dynamics, assess size-class structure, identify spawning strategies and timing, and pinpoint bottlenecks at specific life stages. This basic population information, while simple to collect on more abundant species, becomes exceedingly difficult to collect when take or even handling of fish is not a responsible alternative. Additionally, photogrammetric measurements from a stereo-video camera system were found to be more accurate and precise than diver estimates. Little to no bias was evident (mean error = 0.05 mm) and the level of precision, as measured by the coefficient of variation of the differences among observed and true lengths, was 4.5%, compared to over 10% for divers. Stereo-video camera surveys should increase the consistency of long-term datasets and improve resolution to detect important differences in the length of small-bodied fishes like the Devils Hole pupfish, Cyprinodon diabolis. Stereo-video monitoring at Devils Hole began in March of 2010 and will continue until at least February 2011 with dives being conducted monthly. Preliminary results from the stereo-video surveys including size-class structure and the timing and frequency of cohort recruitment will be presented and discussed.