The effects of electricity on the survival of fish embryos as a means of controlling invasive cyprinids

Samuel A Nutile, Purdue University

Abstract

Asian carp were first introduced into United States waterways in the 1970's when they escaped from aquaculture facilities, and since then they have become extremely well established and are devastating natural ecosystems in these waterways. A variety of efforts have been investigated to control both the spread and population sizes of these invasive fishes, but none of this research has investigated the potential of using electricity to control these species at early life history stages. The effects of electricity on the early life history stages of fishes has been well documented, and survival of the embryos is related to embryo size, exposure duration, voltage gradient, the developmental stage at the time of exposure, and the current type. Therefore, the objectives of this research were to: 1) use three model cyprinid fish species to determine the voltage type (virtual direct current or pulsed direct current), exposure duration, and voltage gradient necessary to cause significantly increased embryo mortality, and determine the most vulnerable developmental stages of the embryos of these species to estimate the effects of electricity on silver carp embryos; 2) test the effects of multiple exposures on the survival of zebrafish (Danio rerio) embryos with different resting intervals between shocking events to determine how multiple exposures affects fish embryo survival; and 3) determine the lethal concentration 50 (LC50) of rotenone to zebrafish embryos to test the combined effects of electricity plus rotenone on zebrafish embryos when applied at concentrations at and below the LC50 value during electroshocking to determine if the simultaneous stressors can result in higher mortality than has been previously seen with electrical field exposures alone. The results of this research are consistent with previous research in that embryo survival across all species tested was related to developmental stage and voltage gradient. Zebrafish embryo survival was also affected by differences in current type and exposure duration. Surprisingly, zebrafish embryos were not affected by multiple exposures to electrical fields. Furthermore, when rotenone was added at values 10 and 100X lower than the LC50, no signs of increased mortality were observed. In terms of controlling Asian carp with electricity at early life history stages, the results of this research are discouraging. If the carp respond the same as the species in this study, then the amount of electricity necessary to cause mortality is impractical in a field application. However, since Asian carp embryos are much larger than the embryos used in this study, lower voltage gradients might cause higher mortality compared to the species studied here. Unfortunately, due to complications with obtaining carp embryos, the number of embryos exposed in this research was minimal, and further testing is necessary to explicitly determine the effectiveness of using electricity as a means of controlling these invasive cyprinids.

Degree

M.S.

Advisors

Goforth, Purdue University.

Subject Area

Aquatic sciences

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