Efficiency of sampling sunfishes using snorkeling in clear, warmwater streams of the south-central United States

The continued evaluation of fish-sampling gears and methods is essential to identify their applicability across environmental conditions and among species. Although limited by visibility, snorkeling has potential advantages relative to other fish-sampling gears in wadeable streams (e.g., minimally intrusive, cost effective, and appropriate in deeper areas). Clear water is common to warm-water streams; however, the use of snorkeling for monitoring stream-fish populations has largely focused on cold-water systems. To assess relative snorkeling efficiency in warm-water streams, we compared standardized single-pass snorkel counts to tow-barge electrofishing abundance estimates for six sunfishes (Centrarchidae) in the Ozark Highlands ecoregion of northwest Oklahoma and southwest Missouri under relatively similar environmental conditions (i.e., clear water, cobble substrates, low-flow conditions). Snorkeling efficiency was variable among sunfishes and consistently low for species with cryptic traits and habitat use. We also did not detect cryptic sunfishes (i.e., a single individual was not encountered) using snorkeling at multiple stream reaches where estimated abundance was > 50 within a 0.5- to 1.0-km stream reach. Our findings indicate that snorkeling has applications for monitoring sunfish populations and assemblages when using an abundance estimator or accounting for imperfect detection; however, it is inappropriate for estimating population size of cryptic sunfishes. We encourage continued research into the applicability of snorkeling to estimate warm-water stream fish abundance.