Best practices to mitigate seabird bycatch in longline, trawl and gillnet fisheries - efficiency and practical applicability
Growing concerns have been raised about incidental capture of seabirds in various fisheries. Here, studies testing measures to prevent seabird bycatch in longline, trawl and gillnet fisheries are reviewed in order to identify the most efficient mitigation methods. There is potential for considerable reductions in mortality rates in most longline fisheries because effective measures have been developed. There is however, no single solution as the efficiency of a measure is specific to each fishery. In demersal longline fisheries where northern fulmar is the dominant seabird captured, streamer lines have proved to virtually eliminate mortality. In the fishery for Patagonian toothfish, where interactions with albatrosses occur, night setting has given considerable bycatch reductions. Night setting has proved to be efficient also in pelagic fisheries, but in areas inhabited by nocturnal and diving birds, this measure should be used in combination with streamer lines and weighted longlines. The main cause of mortality in trawl fisheries is collision with warp and netsonde cables, but studies are fragmentary. Interactions between cables and seabirds have been shown to be rare at times of no offal discharge suggesting that no-discharge policy would virtually eliminate mortality. Streamer lines have proved to effectively reduce cable strikes under offal discharge. Measures to prevent birds from diving into the trawl net meshes have not been tested. Efficient mitigation methods that maintain target fish catch still have to be identified for gillnet fisheries. Future research in longline fisheries should fine-tune the most promising measures for each specific fishery. Effective measures identified for trawl fisheries need to be expanded to and tested in other areas where seabird interactions occur.