Reaction of plaice (Pleuronectes platessa) and cod (Gadus morhua) to low-frequency sound in an experimental tank

Abstract

Anthropogenic sound in the sea is an increasing problem and more knowledge on the influence of sound on fish needs to be collected. For this reason experiments are carried out in an experimental tank 10 m in diameter to examine the reaction of juvenile and adult cod and plaice to sound. Pure tones from the frequency range of offshore wind turbines are artificially emitted in typical wind turbine sound levels of 130 and 140 dB re 1 Pa. A sound gradient in the tank enables the fish to avoid highest sound levels. The number of fish in the vicinity of the sound source is determined in regular time intervals before, during, and after the 24-h period of sound exposure. Changes in numbers of fish can be seen in the periods with and without sound in many experiments. Reactions of plaice are ambiguous, pointing to both avoidance of or attraction to the sound. In the majority of the experiments carried out on cod, avoidance behavior to the sound can be seen with strongest reactions at 25, 60, and 90 Hz. The results indicate potential avoidance behavior of cod to the operational noise of offshore wind farms.