Marine habitat use of black-footed and Laysan albatrosses during the post-breeding season and their spatial and temporal overlap with commercial fisheries

• Main Author: Fischer, Karen Naess
• Other Authors: Roby, Daniel D., Sampson, David B., Suryan, Robert M., Wright, Dawn J., Fisheries and Wildlife, Oregon State University. Graduate School
• Format: Master Thesis
• Language: English; unknown
• Published: Oregon State University
• Subjects: Laysan albatross > Habitat > Alaska > Aleutian Islands; Black-footed albatross > Habitat > Alaska > Aleutian Islands; Black-footed albatross > Alaska > Aleutian Islands > Geographical distribution; Laysan albatross > Alaska > Aleutian Islands > Geographical distribution; Alaska; Aleutian Islands
• Online Access: https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/zg64tp53d

Incidental bycatch in commercial fisheries has been identified as a threat to black-footed albatrosses (Phoebastria nigripes) and Laysan albatrosses (P. immutabilis). Effective long-term conservation of these albatrosses necessitates a thorough understanding of their marine distribution, which marine habitats are selected during foraging, and where they are most likely to interact with fisheries throughout the annual cycle. During August 2005 and July 2006 we captured and satellite-tagged black-footed and Laysan albatrosses at-sea near Seguam Pass, central Aleutian Islands, Alaska (52.08o N, 172.95o W). To quantify habitat use and assess potential risk from bycatch we integrated satellite-tracking data from seven black-footed albatrosses (all in 2005) and 18 Laysan albatrosses (2005: n = 9; 2006: n = 9) with remotely-sensed habitat variables and data on fishing effort and distribution from commercial fisheries in the North Pacific Ocean. We used first-passage time analysis and model selection to identify locations of area-restricted search (ARS), quantify the relationship between area-restricted search and marine habitat variables, and compare and contrast habitats used by the two albatross species. For both species ARS was inversely related to wind speed and depth and positively related to gradients in depth, sea surface temperature, and chlorophyll a concentration. Black-footed albatross ARS was inversely related to sea surface temperature and increased in continental margin habitats (shelf, shelf break, and slope) relative to oceanic habitats; Laysan albatrosses did not exhibit such strong relationships with sea surface temperature and seafloor depth. Area-restricted search for both albatrosses was greater in vertically mixed waters (e.g., coastal upwelling and frontal zones) compared to vertically stratified waters (e.g., oceanic waters, weak frontal boundaries). We found that despite these similarities in habitat-specific area-restricted search in relation to habitat variables, black-footed albatrosses were ...