Interactions between anchovy fisheries and Peruvian boobies revealed by bird-borne cameras and movement loggers
Fisheries threaten marine predator populations through bycatch and competition for the same resources, but may also provide feeding opportunities. Understanding benefits and mitigating impacts, therefore, requires a detailed understanding of fishery interactions. The Humboldt Current system supports the world’s largest single-species fishery (Peruvian anchoveta Engraulis ringens), along with abundant marine predators dependent on these forage fish, including seabirds. We combined bird-borne video cameras and GPS-acceleration-dive loggers to quantify the foraging behaviour of chick-rearing Peruvian boobies Sula variegata around Isla Macabi, Peru, in December 2020 and May 2021. Videos revealed that 18% of 77 Peruvian booby foraging trips included feeding at actively fishing purse seine vessels, diving in and around the nets. Most vessel interactions were close to the colony, and we found no difference in foraging effort (e.g. trip duration) between trips with and without vessel interactions. We recorded fishing effort in the foraging range of the colony using remotely sensed data from the vessel monitoring system accessed via Global Fishing Watch, finding more frequent interactions and catch depredation when fishing effort was high near the colony. We found no evidence that birds expended additional energy (e.g. dynamic body acceleration) or travelled to different locations to reach vessels. We emphasise the value of combining high-resolution movement and video loggers with remotely sensed fisheries data to monitor seabird-fishery interactions in detail, rather than just spatio-temporal overlap, and assess the potential for competition and bycatch. Threatened seabird populations may benefit from no-take zones or reduced fishing effort in core foraging areas of colonies.
Not tunas, but techniques broadly applicable.