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A new study on the overlap of the at-sea ranges of Black-footed Phoebastria nigripes and Laysan P. immutabilis Albatrosses captured in Alaska (Karen Fischer et al. 2009) has found that Black-footed Albatrosses have a higher potential for fisheries interactions as a result of spending more time in coastal waters where fishing effort is highest.

Albatrosses of both species were satellite-tagged at-sea in the Central Aleutian Islands, Alaska, USA and tracked during the post-breeding season, July- October 2005 and 2006. Satellite tracking data was integrated with data on fishing effort and distribution from commercial fisheries in the North Pacific.  In Alaskan waters, fishing effort occurred almost exclusively within continental shelf and slope waters.  Potential fishery interaction for Black-footed Albatrosses, which most often frequented shelf-slope waters, was greatest with Sablefish Anoplopoma fimbria longline and pot fisheries and with the Pacific Halibut Hippoglossus stenolepsis longline fishery. In contrast, Laysan Albatrosses spent as much time over oceanic waters beyond the continental shelf and slope, overlapping less with fisheries in Alaska than did Black-footed Albatrosses.

Regionally, Laysan Albatrosses had the greatest potential fishery interaction with the Atka Mackerel Pleurogrammus monopterygius trawl fishery in the Western Aleutian Islands and the Sablefish pot fishery in the Central Aleutian Islands.  Black-footed Albatrosses ranged farther beyond Alaskan waters than did Laysan Albatrosses, overlapping west coast Canada fisheries and pelagic longline fisheries in the subarctic transition domain; Laysan Albatrosses remained north of these pelagic fisheries.

Due to inter-specific differences in oceanic distribution and habitat use, the overlap of fisheries with the post-breeding distribution of Black-footed Albatrosses is greater than that for Laysan Albatrosses, highlighting inter-specific differences in potential vulnerability to bycatch and risk of population-level impacts from fisheries.

The results of this study are consistent with bycatch statistics and previous studies which indicate that a higher proportion of the Black-footed Albatross population is being impacted by fisheries bycatch compared to the more numerous Laysan Albatross. Notably, the authors found a strong male-bias in their at-sea captures of both species and suggest that either sex-segregated foraging occurs (which is not supported by previous tracking work) or that gender differences in behaviour or size may also lead to competitive displacement of females by males behind vessels.  Potential sex-biased mortality in fisheries bycatch could have significant population-level consequences for both species.

Several upcoming studies that integrate year-round tracking data with fisheries overlap information will soon be available and will provide a greater understanding of the potential bycatch risk for all three of the North Pacific albatrosses.

Reference

Fischer, K.N., Suryan, R.M., Roby, D.D. & Balogh, G.R. 2009.  Post-breeding season distribution of Black-footed and Laysan Albatrosses satellite-tagged in Alaska: inter-specific differences in spatial overlap with North Pacific fisheries.  Biological Conservation 142: 751-760.