Pingers as a potential deterrent tool to mitigate Burmeister’s porpoise (Phocoena spinipinnis) bycatch while foraging nocturnally in the Humboldt Current System: a pilot study

Fisheries bycatch is one of the main threats for porpoise species worldwide. In the Humboldt Current system of northern Chile, the elusive Burmeister’s porpoise ( Phocoena spinipinnis ) inhabits the coastal waters of Mejillones Bay and suffers bycatch mortality in purse seine fishing nets and coastal gillnets. In order to mitigate bycatch of this near-threatened species, this study aimed to (1) analyze the diurnal and nocturnal acoustic behaviors of the Burmeister’s porpoise and (2) evaluate the potential of banana pingers as acoustic deterrent tools. For 27 days during austral summer, a full wave form capture porpoise detector was anchored 7 m above sea level in Mejillones Bay where Burmeister’s porpoises are frequently observed. During this time, the detector registered acoustic activity continuously over 13 days, and a banana pinger deployed over 100 m away from the detector emitted high frequency sounds continuously for 14 days. The results show that the number of clicks and detection-positive minutes were significantly higher while the inter-click intervals and high click rate feeding buzz were significantly lower at night, indicating that Burmeister’s porpoises forage mainly nocturnally in this bay. With pingers present, the probability of detection of Burmeister’s porpoise acoustic activity decreased by 20%, suggesting that pingers could be an effective tool to avoid Burmeister’s porpoise mortality in fishing nets. Future studies should implement pingers in artisanal purse seine fishing nets and coastal gillnets in order to mitigate Burmeister’s porpoise bycatch in northern Chile.