Sound affects behavior of captive zebrafish: Always consider the potential for acoustic effects on your laboratory tests

Abstract

Sounds generated by human activities have increased ambient noise levels underwater, both in natural habitats and in captivity. Fishes may be affected through disturbance, deterrence and masking. Two different set-ups were used to test individual zebrafish response behavior to experimental sound exposure. In the first, an elongated fish tank was used to create a gradient of sound pressure levels. In the second, a dual tank set up was used to create a more discrete acoustic transition. Response patterns indicated initial anxiety in both experiments: startle responses followed by a general slow-down and sometimes complete freezing. Lateral displacement away from speakers was not observed, except for avoidance of the area directly in front of the active speaker in the second experiment. At other places, sound fields likely varied in such a complex way that there were no cues available for fish to sense the sound source direction. Nevertheless, our data showed that sounds can have significant effects on swimming patterns which likely reflect anxiety in captive zebrafish. Many laboratories are noisy and sounds from machines and doors transmit easily through concrete floors into aquaria. Consequently, investigators of fish behavior should always consider the potential for acoustic effects on laboratory tests.