The responses of Atlantic cod (Gadus morhua L.) to ultrasound-emitting predators: stress, behavioural changes or debilitation?

• Published in: Journal of Experimental Biology
• Main Authors: Schack, Henriette B., Malte, Hans, Madsen, Peter T.
• Format: Text
• Language: English
• Published: Company of Biologists 2008
• Subjects: Research Article; atlantic cod; Gadus morhua; toothed whales
• Online Access: http://jeb.biologists.org/cgi/content/short/211/13/2079; https://doi.org/10.1242/jeb.015081

A previous study has reported that Atlantic cod can be conditioned to detect ultrasonic sound pulses of high intensity. This capability has been proposed as a mean for detection and avoidance of echolocating toothed whales that emit intense ultrasonic clicks. In this study, we use acoustic playbacks to test the hypotheses that unconditioned cod can detect and respond to intense ultrasound from toothed whales and from echosounders. Intense ultrasound exposure of 210 dB re. 1μPa (pp) did not cause a short-term stress response in the form of bradycardia in unconditioned cod. Free-swimming cod exposed to ultrasonic clicks and echosounder pulses with received levels of more than 204 dB re. 1 μPa (pp) did not elicit flight responses as seen in ultrasound detecting Alosinae. Furthermore, we tested the debilitating effects of high intensity ultrasound on swimming cod with no detected changes in swimming ability when exposed to more than 213 dB re. 1 μPa (pp). It is concluded that intense ultrasound exposure induces neither an antipredator nor a stress response in Atlantic cod, and that echosounder pulses and biosonar clicks therefore most probably play no ecophysiological role in wild cod populations.