Bird Bycatch in Longline Fisheries in the South Atlantic

1. Background and Objective of the Study

Accidental mortality of seabirds due to pelagic longline fishing poses a major threat to many endangered populations (particularly albatrosses and petrels). This study develops an ecological risk assessment (using the EASI-Fish model) to compare the effectiveness of mitigation measures currently specified by the International Commission for the Conservation of Atlantic Tunas (ICCAT) with the best-practice guidelines recommended by the Working Group on Seabird Bycatch of the Agreement on the Conservation of Albatrosses and Petrels (ACAP).

2. Species Assessed

The study focuses on five populations of four species that forage in the South Atlantic and nest primarily in the British Overseas Territories (UKOTs):

    - The Atlantic Yellow-nosed Albatross (Thalassarche chlororhynchos)

    - The Tristan Albatross (Diomedea dabbenena)

    - The Screaming Albatross (Diomedea exulans)

    - The White-chinned Petrel (Procellaria aequinoctialis) – assessed for two populations (South Georgia and the Prince Edward Islands)

3. Key Findings and Mortality Reductions

Updating the specifications for ICCAT’s current mitigation measures to reflect ACAP’s best-practice guidelines would potentially reduce seabird mortality by 41 to 86 percent (compared to vessels using two of the three basic options). The simultaneous implementation of the three measures recommended by ACAP as current best practices (branch line weighting, night fishing, and bird-scaring lines/tori lines) would reduce seabird mortality by 72 to 93%. This is the most effective configuration (ACAP4 scenario). Branch line weighting has been found to be the single most important factor explaining the differences in bycatch reductions across scenarios, due to major differences in specifications between ICCAT and ACAP recommendations. When used alone, these devices perform comparably to other ACAP best-practice guidelines and represent a highly beneficial alternative.

4. Key Recommendations Made by the Authors

ICCAT should consider mandating the simultaneous use of all three mitigation measures, as specified in ACAP’s best practices, as the most appropriate management measure for seabirds. The best-practice guidelines should be followed throughout the range of vulnerable species, as many populations (particularly juveniles and immature individuals) face a substantial risk of bycatch north of 25°S.