Sampling Stream Centrarchids: Comparing Electrofishing and Underwater Observation

We compared electrofishing and underwater observations as different methods for estimating population characteristics of centrarchids in a medium-sized warmwater stream in Missouri. We evaluated how well each method determined length-frequency distribution of smallmouth bass (Micropterus dolomieui), rock bass (Ambloplites rupestris), and longear sunfish (Lepomis megalotis). Underwater observation was the more accurate technique, producing length-frequencies more typical of a catch curve. When compared to underwater observations, electrofishing sampled the largest size class of fish effectively, but not the smallest size classes. Electrofishing efficiency was species specific and was related to habitat preferences and fish behavior. Correction factors, developed from observational data, can be used to increase the accuracy of electrofishing data. An evaluation of recapture methods from mark-recapture analysis, after initial marking by electrofishing, showed recapture by observation to be no better than recapture by electrofishing.

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