Multipass electrofishing sampling efficiency for stream crayfish population estimates
We estimated the efficiency of electrofishing for collecting crayfishes in southern Appalachian Mountain streams (Alabama, USA). We conducted electrofishing depletion surveys at 20 sites in five large, species-rich streams in two drainages. We collected five crayfish species during the depletion surveys. On average, catchability was 34%, with depletion surveys collecting 73% of the individuals that were estimated to reside within stream sections. Catchabilities were lower for pass 1 than for the subsequent passes in 21% of the depletion surveys. The number of species that was collected increased during the second electrofishing pass, indicating that conducting two electrofishing passes may be more effective than a single electrofishing pass is for estimating the richness of crayfish species. Crayfish catchability by electrofishing was higher in streams with higher conductivities, longer crayfish, higher water temperatures, and lower percentages of adult males. Our results show that multipass electrofishing can precisely assess population density for various crayfish species in species-rich, large-stream habitats and that multipass electrofishing provides more precise estimates of species richness for crayfish than single-pass electrofishing does.