Assessing the susceptibility of female black-footed albatross (Phoebastria nigripes) to longline fisheries during their post-breeding dispersal: an integrated approach

摘要

Albatross movements and foraging grounds during the post-breeding dispersal are poorly understood, despite their important conservation implications. We tracked four female black-footed albatrosses (Phoebastria nigripes) for 100 days during their summer (July-September, 1997-1999) post-breeding dispersal off California, and compared their movements to the distribution of fishing effort from the Japanese Eastern Pacific Ocean (EPO) longline fishery. The tracked birds foraged largely along the transition zone between the California Current and the Central Pacific Gyre, and spent 25, 24, and 51% of their time at sea within the 200-mile exclusive economic zones (EEZs) of the USA and Mexico, and the high seas (international waters) respectively. The satellite-tracked birds occupied subtropical waters (18-20 degreesC) targeted by longline fisheries for tuna (Thunnus spp.) and broad-bill swordfish (Xiphias gladius), and ranged disproportionately farther during daylight hours, when tuna fisheries operate. The available data suggest that albatrosses overlap temporally and spatially with longline fisheries in the northeast Pacific Ocean. However, this research cannot directly evaluate whether black-footed albatross bycatch occurs in these fisheries. The coarse temporal (monthly) and spatial (1degrees x 1degrees) resolution of the fisheries data, and the dynamic nature of the fishing effort inhibited a fine-scale analysis of albatross overlap with longline fisheries. While we documented substantial spatial overlap between albatross distributions and the Japanese EPO longline fishing effort during the 1980s, we found no co-occurrence during the 1990s. This study illustrates the value of satellite telemetry to assess national conservation responsibilities, and to identify potential interactions of protected species with fisheries not currently monitored by observer programs. Furthermore, our results underscore the need to exercise caution when interpreting satellite telemetry data for conservation purposes, because of the highly dynamic nature of pelagic fisheries.