Scare fish-eating birds from areas to reduce conflict
Overall effectiveness category Evidence not assessed
Number of studies: 0
Background information and definitions
Commercial fisheries have expanded dramatically across the world since the 1960s, and are having increasing direct impacts on seabirds worldwide. Commercial longline, trawl and gillnet fisheries are responsible for the deaths of hundreds of thousands of seabirds each year, threatening the survival of a number of species, especially albatrosses.
Longline fleets set more than one billion hooks each year and up to 300,000 seabirds, including 100,000 albatrosses, are killed on longlines as they scavenge for bait and offal and are accidentally caught on the fishhooks and drowned. This form of bycatch is now the single greatest threat to albatrosses. All 22 albatross species are classed as globally threatened or Near Threatened.
Trawl fisheries are also a threat, with birds killed when they are hit by the powerful cables that attach the trawl net to the vessel, and by being entangled by the net as they scavenge for fish.
Gillnets – static curtains of netting designed to entangle fish by their gills – can be responsible for the accidental entanglement of large numbers of pelagic birds. Despite a ban on their use in the high seas, commercial gillnet fisheries continue to operate in territorial and coastal waters around the world, where they pose a significant threat to numerous seabird populations, especially ‘pursuit-diving’ species, such as divers (loons), grebes, sea ducks, auks and cormorants.
This bycatch is extremely detrimental to bird populations, but is also expensive for fishermen, as each bait taken by a bird is one lost for catching fish. Methods to prevent bycatch are therefore also likely to increase profits. Both conservation-based and commercial fisheries organisations are now working together to try and uncover which methods are the most effective and then to ensure that every boat employs them.
A literature review in 2000 (Melvin & Robertson 2000) argued that much of the research into bycatch is confused and non-standardised, with different methodologies being used and experiments often uncontrolled. Bycatch can often vary hugely from one voyage to the next and from year to year, due to movements of birds and changes in fish stocks, but also because of factors, such as the phase of the moon, which alter the effectiveness of, for example, setting lines at night. Evidence from single-year comparisons or uncontrolled tests therefore need to be treated with caution.
Melvin, E.F. and Robertson, G. 2000. Appendix 3. Seabird mitigation research in longline fisheries: status and priorities for future research and actions. In: Cooper, J. (Ed.). Albatross and Petrel Mortality from Longline Fishing International Workshop, Honolulu, Hawaii, USA, 11–12 May 2000. Report and presented papers. Marine Ornithology, 28, 179