The roles of organochlorine contamnants and fisheries bycatch in recent population changes in black-footed and Laysan albatrosses in the North Pacific Ocean

Organochlorine contaminants were measured in Laysan and Black-footed Albatrosses nesting at Midway Atoll, Hawaiian Leeward Islands. Samples from Black-footed Albatrosses were two to three times more contaminated with polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin equivalents (TCDD-EQs) and the DDT group chemicals than were samples from Laysan Albatrosses. Black-footed Albatrosses were sufficiently contaminated to be at slight risk from eggshell thinning and subtle embryonic effects that increase risks of terata and decrease egg viability; observed hatching success was lower and egg crushing greater in Black-footed Albatrosses than Laysan Albatrosses. Organochlorine contamination probably reduced productivity by 2-3% in the Black-footed Albatross population. No contaminant effects were found in Laysan Albatrosses. Estimates of the effect of adult loss and widowing from fisheries bycatch revealed productivity reductions of 17.6% in Laysan Albatrosses and 27.15% in Black-footed Albatrosses, confirming the serious impact of fisheries on these species of albatrosses. Black-footed Albatross census data indicate a recent decrease in populations since the 1980s. Bycatch accounts for almost all (90%) of the recent productivity decrease in this population and contaminants were believed to cause about 10%. The Black-footed Albatross population is expected to decrease slowly owing to these mortalities. The Laysan Albatross population demonstrated no contaminant-related effects, and is increasing slowly in spite of increased bycatch in the last 20 years.