Longline fishing

:"For other meanings of "longline", see longline."Longline fishing is a commercial fishing technique that uses hundreds or even thousands of baited hooks hanging from a single line. Swordfish, tuna, halibut, sablefish and many other species are commonly targeted by longliners.

In some unstable fisheries, such as that of Patagonian toothfish, fishermen may be limited to as few as 25 hooks per line. In contrast, large commercial longliners in certain robust fisheries of the Bering Sea and North Pacific generally run over 2500 hand-baited hooks on a single series of connected lines many miles in length. externalimage
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http://www.afma.gov.au/information/students/methods/pelagic.htm Pelagic longline]

http://www.afma.gov.au/information/students/methods/demersal.htm Demersal longline] Longlines can be set to hang near the surface (pelagic longline) to catch fish such as tuna and swordfish or along the sea floor (demersal longline) for groundfish such as halibut or cod. Longliners fishing for sablefish, also referred to as black cod, will occasionally set gear on the sea floor at depths exceeding 600 fathoms using relatively simple equipment. Longlines with traps attached rather than hooks can be used for crab fishing in deep waters.

Generally, longline fishing is environmentally friendly with no destructive impact on bottom habitats, good selectivity and low fuel consumption. The exception is that longline fishing can be prone to the incidental catching and killing of seabirds and sea turtles. [Valdemarsen, John W [http://www.oceansatlas.org/world_fisheries_and_aquaculture/html/issues/ecosys/selectgear/incidental_catch.htm "Incidental catch of seabirds in longline fisheries"] Fishery Technology Service]

Incidental catch

Longline fishing is controversial in some areas because of by-catch. Methods to mitigate such incidental mortality have been developed and successfully implemented in some fisheries. Seabirds can be particularly vulnerable during the setting of the line. Mitigation techniques include the use of weights to ensure the lines sink quickly, the deployment of streamer lines to scare birds away from the baited hooks as they are deployed, setting lines only at night with ship lighting kept low (to avoid attracting birds), limiting fishing seasons to the southern winter (when most seabirds are not feeding young), and not discharging offal while setting lines.

However, gear modifications do not eliminate by-catch of other species and the controversy continues. In March 2006, the Hawaii longline swordfish fishing season was closed due to excessive loggerhead sea turtle by-catch after being open only a few months, despite using modified circle hooks which attempt to reduce by-catch.

Of the 21 albatross species recognised by IUCN on their Red List, 19 are threatened, and the other two are "near threatened". [IUCN, 2004. [http://www.iucnredlist.org/search/search.php?freetext=Albatross&modifier=phrase&criteria=wholedb&taxa_species=1&redlistCategory%5B%5D=allex&redlistAssessyear%5B%5D=all&country%5B%5D=all&aquatic%5B%5D=all&regions%5B%5D=all&habitats%5B%5D=all&threats%5B%5D=all&Submit.x=104&Submit.y=16 Red List: Albatross Species] . Retrieved July 27, 2007.] Two species (as recognised by the IUCN) are considered critically endangered: the Amsterdam Albatross and the Chatham Albatross. One of the main threats is commercial long-line fishing, [Brothers NP. 1991. "Albatross mortality and associated bait loss in the Japanese longline fishery in the southern ocean." "Biological Conservation" 55: 255–268.] as the albatrosses and other seabirds which will readily feed on offal are attracted to the set bait become hooked on the lines and drown. An estimated 100,000 albatross per year are killed in this fashion. Unregulated pirate fisheries exacerbate the problem.

Notes

References

* Brothers, N P; Cooper, J and Lokkeborg S (1999) "The Incidental catch of seabirds by longline fisheries". Rome, FAO Fisheries Circular No 937.

External links

* [http://www.seafood.co.nz/n286,55.html Long lining] , New Zealand Seafood Industry Council
* Johnson, Douglas H; Shaffer, Terry L and Gould, Patrick J (1990) [http://www.npwrc.usgs.gov/resource/birds/icatch/index.htm "Incidental Catch of Marine Birds in the North Pacific High Seas Driftnet Fisheries"] U.S. Geological Survey.
* Valdemarsen, John W [http://www.oceansatlas.org/world_fisheries_and_aquaculture/html/issues/ecosys/selectgear/incidental_catch.htm "Incidental catch of seabirds in longline fisheries"] UN Atlas of the Oceans: Fishery Technology Service.