TY - JOUR
T1 - The fine-scale behavior of harbor porpoises towards pingers
AU - Brennecke, Dennis
AU - Siebert, Ursula
AU - Kindt-Larsen, Lotte
AU - Midtiby, Henrik Skov
AU - Egemose, Henrik Dyrberg
AU - Ortiz, Sara Torres
AU - Knickmeier, Katrin
AU - Wahlberg, Magnus
PY - 2022
Y1 - 2022
N2 - High numbers of harbor porpoises (Phocoena phocoena) end up as bycatch in gillnets every year. Acoustic alarms (pingers) have been demonstrated to be an efficient mitigation tool to prevent bycatch of this species; however, little is known about the behavioral reactions of wild porpoises to pingers. This knowledge is important for optimizing the design and use of pingers. We tracked 16 wild porpoises with a drone and recorded their behavior before and during exposure to pinger sounds. Range from the pinger to the porpoise was 158–797 m when the pinger was first activated. In four of the exposures, with pinger-to-porpoise ranges of 199–521 m, reaction to the pinger was strong avoidance behavior with increased swimming speed heading away from the pinger. Average number of surfacings decreased from 3.4 surfacings/min before pinging to 2.8 surfacings/min during pinging. Eight animals were lost from the drone’s field of view as soon as the pinger playback started, indicating that they were either diving deep or speeding away from the area very rapidly. Four animals did not respond to pinger sounds, demonstrating a diversity in the behavioral response. Neither the behavior of porpoises (i.e., foraging, socializing and traveling) before sound exposure, the animal’s initial direction in relation to the sound source, nor the porpoise-to-pinger range affected their reaction in relation to the pinger. Pingers can cause very strong aversive reactions in harbor porpoises, which explains their efficiency in reducing bycatch. The strong aversive reactions may suggest that pinger use should be limited to critical time periods and regions, or that more focus needs to be put on developing acoustic devices which cause less severe behavioral reactions. At the same time, this study shows that 25 % of animals may not react to pinger sounds, indicating a great diversity in behavioral responses.
AB - High numbers of harbor porpoises (Phocoena phocoena) end up as bycatch in gillnets every year. Acoustic alarms (pingers) have been demonstrated to be an efficient mitigation tool to prevent bycatch of this species; however, little is known about the behavioral reactions of wild porpoises to pingers. This knowledge is important for optimizing the design and use of pingers. We tracked 16 wild porpoises with a drone and recorded their behavior before and during exposure to pinger sounds. Range from the pinger to the porpoise was 158–797 m when the pinger was first activated. In four of the exposures, with pinger-to-porpoise ranges of 199–521 m, reaction to the pinger was strong avoidance behavior with increased swimming speed heading away from the pinger. Average number of surfacings decreased from 3.4 surfacings/min before pinging to 2.8 surfacings/min during pinging. Eight animals were lost from the drone’s field of view as soon as the pinger playback started, indicating that they were either diving deep or speeding away from the area very rapidly. Four animals did not respond to pinger sounds, demonstrating a diversity in the behavioral response. Neither the behavior of porpoises (i.e., foraging, socializing and traveling) before sound exposure, the animal’s initial direction in relation to the sound source, nor the porpoise-to-pinger range affected their reaction in relation to the pinger. Pingers can cause very strong aversive reactions in harbor porpoises, which explains their efficiency in reducing bycatch. The strong aversive reactions may suggest that pinger use should be limited to critical time periods and regions, or that more focus needs to be put on developing acoustic devices which cause less severe behavioral reactions. At the same time, this study shows that 25 % of animals may not react to pinger sounds, indicating a great diversity in behavioral responses.
KW - Drone
KW - Phocoena phocoena
KW - Pinger
KW - Acoustic deterrent
KW - Bycatch
U2 - 10.1016/j.fishres.2022.106437
DO - 10.1016/j.fishres.2022.106437
M3 - Journal article
SN - 0165-7836
VL - 255
JO - Fisheries Research
JF - Fisheries Research
M1 - 106437
ER -