167 individuals versus millions of hooks: bycatch mitigation in longline fisheries underlies conservation of Amsterdam albatrosses
Résumé
1. Industrial fisheries represent one of the most serious threats worldwide to seabird conservation. Death of
birds in fishing operations (i.e. bycatch) has especially adverse effects on populations of albatrosses, which have
extremely low fecundity.
2. The single population worldwide of Amsterdam albatross (Diomedea amsterdamensis) comprises only 167
individuals and risks considerable decline over the mid-term from additional mortality levels potentially induced
by fisheries. The priority actions listed in the current conservation plan for this species included characterizing
the longline fisheries operating within its range, dynamically analysing the overlap between albatrosses and these
fisheries, and providing fisheries management authorities with potential impact estimates of longline fisheries on
the Amsterdam albatross.
3. During all life-cycle stages and year quarters the birds overlapped extensively with fishing effort in the
southern Indian and Atlantic oceans. Fishing effort, and consequently overlap score (calculated as the product
of fishing effort and time spent by the birds in a spatial unit) was highest in July–September (45% of the hooks
annually deployed). Just three fleets (Taiwanese, Japanese and Spanish) contributed to >98% of the overlap scores
for each stage (72% from the Taiwanese fleet alone, on average). Daily overlap scores were higher for the
non-breeding versus the breeding stages (3-fold factor on average).
4. Based on previous bycatch rates for other albatross species, this study estimated that longline fisheries
currently have the potential to remove ~2–16 individuals (i.e. ~5%) each year from the total Amsterdam
albatross population, depending on whether bycatch mitigation measures were or were not systematically
employed during the fishing operations.
5. Recent bycatch mitigation measures may be instrumental in the conservation of the Amsterdam
albatross. This study suggests three further key recommendations: (1) to focus conservation efforts on the
austral winter; (2) to require all operating vessels to report ring recoveries; and (3) to allocate special
regulation of fishing operations in the areas of peak bycatch risk for the Amsterdam albatrosses.