Albatrosses redirect flight towards vessels at the limit of their visual range

摘要

Seabird-fishery interactions are important to seabird ecology and conservation since some species obtain a significant amount of food from fisheries, but mortality from bycatch is a primary cause of population declines in several species. While the availability of high resolution GPS data for both seabirds and vessels over the past few years has allowed analyses of fine-scale behavioural responses of seabirds near fishing vessels, little information is available on the distance at which seabirds respond to vessels. Indeed, previous studies have focused on the foraging behaviour of individuals within the vicinity of vessels but have not considered the approach phase of birds. Here we provide such an estimate by examining changes in the flight direction of GPS-tracked wandering albatrosses breeding on the Crozet Islands in response to the toothfish fishing fleet operating around the breeding grounds, monitored using GPS vessel monitoring system data. We show that although we detect increases in feeding behaviour only when albatrosses are within 3 km of boats, they display clear changes in flight direction, towards vessels, at distances up to 30 km. This distance is nearly 3 times as large as previous estimates, almost reaching the theoretical maximum visual range of an albatross. We discuss these results in the light of previous estimates, and pinpoint factors likely to affect the attraction distance. We suggest that this simple estimate of attraction distance could be investigated in other seabird-fishery systems, to improve our understanding of the factors affecting seabird interaction behaviour, and thus better predict when overlap will lead to interactions.