The impact of longline fishing on the seabirds breeding on Marion Island

Doctoral Thesis


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University of Cape Town

This study describes the impact of longline fishing on the seabirds breeding on the sub-Antarctic Prince Edward Islands. The development of a demersal longline fishery for Patagonian toothfish Dissostichus eleginoides close to the islands with almost complete observer coverage during the study allowed a detailed examination of the impacts of this fishery. The vast majority of seabird mortalities were adult males that were breeding at the time they were killed. White-chinned petrels Procellaria aequinoctialis were killed most frequently, but albatrosses and giant petrels were also killed when lines were set in the daytime. Birds were killed almost exclusively during their breeding season, and albatrosses were caught closer to the islands than whitechinned petrels. It is estimated that between 8 500 and 18500 birds could have been killed between 1996-2000, mostly due to high levels of Illegal Unregulated and Unreported (IUU) fishing. This is likely to have a significant impact on the breeding populations of several species of seabirds breeding on the Prince Edward Islands. A large increase in the amount of fishing gear found next to seabird nests as well as fishery-derived items in the diets of wandering albatrosses was recorded concurrent to the development of the toothfish fishery around the Prince Edward Islands. There was also an increase in the number of observed seabird entanglements in fishing gear and mortalities due to the ingestion of fishing gear.

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