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Seabird Research: Effects of Increases in Oceanographic Variability

Research conducted for the AFSC by Dr. Ann Edwards, National Research Council research associate, suggests that the anticipated increase in oceanographic variability in the North Pacific due to global climate change may cause both a decline in the reproductive success of the Laysan albatross and possibly the black-footed albatross and an increase in albatross bycatch rates in Alaskan fisheries.

Based on stable isotope analyses of feathers, data from reproductive plots monitored by the U.S. Fish and Wildlife Service (USFWS), and published information on albatross movements, it appears that for the Laysan albatross, the most successful breeders forage almost exclusively in deep, mid-oceanic waters, especially within the North Pacific Transition Domain, even during the nonbreeding season. On the other hand, less successful breeders and nonbreeders also forage along continental shelves, including those of Alaska.

When marine habitats change due to oceanographic variability (e.g., when a distinct oceanographic feature such as the North Pacific Chlorophyll Front becomes more variable, as it did during the el Nio year of 1998), food appears to become less available to Laysan albatrosses (and possibly black-footed albatrosses), forcing breeders to forage farther from their breeding colonies, perhaps in unfamiliar waters. As travel distances increase, evidence from other albatross species indicates that reproductive success declines.

Large-scale shifts in foraging location are important and relevant to concerns about seabird bycatch because the highest seabird bycatch rates for Alaskan waters since 1993 occurred in 1998. Thus, as habitat quality deteriorated in the central North Pacific in 1998, it appears that more Laysan albatrosses may have travelled to Alaskan waters to feed, increasing incidental mortality.

Dr. Edwards' results suggest links exist between anticipated increases in oceanographic variability, changes in foraging distributions, lower albatross reproductive rates, and higher bycatch rates of albatrosses in Alaskan waters. Dr. Edwards presented these results in December 2007 at the First International Symposium of Climate Effects on Oceanic Top Predators (CLIOTOP), a GLOBEC program.

By Ann Edwards

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