Harbor porpoise (Phocoena phocoena) reactions to pingers

Abstract

The use of acoustic alarms (pingers) has been mandated in several gill net fisheries around the world. Even though pingers have shown to reduce the incidental catch there are still questions to be answered in relation to effective range, habituation and displacement. In the present studies, the vocalization behavior of porpoises was recorded in response to two different pingers, AQUAmark100 (20–160 kHz) and AQUAmark300 (10 kHz). The Scottish experiment included an AQUAmark100 pinger running in on/off cycles. The pinger was placed in an array of acoustic click detectors (C‐PODs) spaced at different distances from the pinger. In Denmark, three experiments were conducted. One had the same AQUAmark100 pinger placed in a C‐POD array. The second and third experiment used an AQUAmark300 pinger running in on/off cycles. Both trial results of the AQUAmark100 revealed significant pinger reduction effects at 0, 200, and 400 m distance; however, the vocalization behavior reveal no signs of habituation. The studies of the AQUAmark300 revealed a significant pinger effect at 0 m distance and either none or 17% reduction at 300 m distance. At one station, however, habituation effects were found indicated by an increase in clicks over time. These results are important in relation to pinger use and thus fisheries management.

Will harbor porpoises (Phocoena phocoena) be deterred by a pinger that cannot be used as a “dinner bell” by seals?

“…This might suggest that porpoises were not distributed differently on the inshore and offshore side of the experimental pinger station, respectively. Kindt‐Larsen et al (2019) logged porpoise click trains using T‐PODS anchored at different distances from Aquamark 100 and Aquamark 300 pingers, with a similar experimental setup. Their study found that the distribution of porpoises might have influenced the results.…”

Towards a new understanding of elasmobranch hearing

“…Fishing hooks equipped with different types of magnets (neodymium-iron-boron or barium-ferrite) have been successful at catching fewer elasmobranch species compared to control fishing hooks without magnets, showing promise for the potential decrease of fishing bycatch (O'Connell et al 2011b). Sound has shown promise in deterring cetaceans (Culik et al 2001;Kindt-Larsen et al 2019), and teleosts (Kastelein et al 2007) but much more research needs to be done on elasmobranchs in a field setting to determine the potential of acoustic cues in bycatch avoidance (Jordan et al 2013;Ryan et al 2018).…”

The diel pattern in harbour porpoise clicking behaviour is not a response to prey activity

“…However, the fact that clicks are produced almost continuously and that animals are constantly moving around has made PAM a very important tool for studying this species in the field. It is also widely used to successfully assess the impact on porpoises from many man-made activities, such as noise from coastal wind farms 1 , 16 – 19 and deterrent signals intended to keep them away from gill nets 20 – 24 .…”