An Evaluation of Fish Electrofishing Capture Efficiency and Sample Designs for Wadeable Warmwater Streams

The AFS standardized designs for estimating the composition of fish communities in wadeable warmwater streams includes maximum effort designs, where samples are collected from a single long stream reach and quadrat based designs, where samples are collected from several smaller reaches. I evaluated the efficacy of each design using empirical simulations to assess the effect of incomplete capture on estimates of fish community composition and biotic integrity. Simulation results indicated that estimates of fish community composition and biotic integrity were consistently underestimated using maximum effort approaches. Underestimates also were related to stream size, habitat characteristics (stream depth, turbidity, and current velocity), and fish community structure. On average, the number of species was underestimated by 4.1 (26.5%), 4.7 (23.5%), and 7.8 (30.0%) in small, medium, and large size streams, respectively. In contrast, estimates of fish community composition obtained with the quadrat design and multi-species occupancy estimators were generally unbiased. Sampling effort and the number of fish handled also were lower for the quadrat design relative to the maximum effort designs suggesting that field crews could sample a greater number of streams with the quadrat design.