首页|Estimating Body Conductivity and Immobilization Threshold in Fish
Estimating Body Conductivity and Immobilization Threshold in Fish
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NSTL
Wiley
Abstract The body conductivity of fish (Cf; μS/cm) and the power density causing threshold immobilization (Dm; μW/cm3) play a critical role in determining electrofishing success. My aim was to compare two methods for estimating Cf and Dm: the response‐threshold method using live Rainbow Trout Oncorhynchus mykiss (12–15?cm TL) and the direct‐measure method using the carcasses of the same fish. The estimates were compared to values from other published studies. I also evaluated the effect of electric field constriction (e.g., depth effect) on Cf and Dm in tanks with water : fish cross‐sectional area ratios of 6:1, 25:1, and 100:1. The resulting data conformed to theory for both methods; that is, Cf and Dm increased with decreasing tank size because field constriction forced more electric current through a fish. Estimates of Cf and Dm by both methods were similar in the two larger tanks (25:1 and 100:1). I suggest a standard Cf value of 60 μS/cm for Rainbow Trout if they are the target species. This value is near the low end of a cluster of published values for various fishes (50–160?μS/cm) that are within cross‐sectional ratios of 20:1 to 100:1. A standard value for Dm cannot be recommended due to variation caused by electrical output and fish size and species. The direct‐measure method proved superior to the response‐threshold method because it requires fewer fish for estimates of Cf and Dm, does not depend on subjective determination of threshold in live fish, and provides information on water‐to‐fish power transfer efficiency.
NSTL
Wiley
