Evaluation of Prepositioned Areal Electrofishing Devices and Fixed Underwater Videography for Characterizing Riverine Fish Assemblages

Prepositioned areal electrofishing devices (PAEDs) are used to evaluate microhabitat use by fishes because they serve to minimize fright biases associated with active electrofishing.  Similarly, fixed underwater videography (FUV) is used to minimize the effect of observers on fish behavior.  Accordingly, we postulated that FUV may be used separately or in conjunction with PAEDs to sample riverine fishes with equal accuracy while minimizing bias from gear or observers.  Furthermore, we sought to determine an appropriate “set time” for PAEDs.  Estimates of taxonomic occurrence generated by PAED and FUV data were evaluated across 15 sampling locations from the Kootenai River, Idaho.  More fish were sampled with FUV than PAEDs at any given location but fish identification was imprecise (i.e., classified to higher taxonomic levels).  An appropriate set time for PAEDs was difficult to determine due to infrequent and erratic observations.  However, our results suggest that PAEDs should be set for a minimum of 10 minutes before applying electricity.  Both gears provide measures of taxonomic occurrence, but logistical and financial constraints should be considered when selecting between these gears.  Results from this study provide preliminary information on the effectiveness of each gear type as it relates to characterizing riverine fish assemblages.