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In parts of the Pacific and Indian Ocean such as the Maldives, billfishing, particularly for swordfish, is an important component of subsistence fishing.

Recreational fishing

Billfish are among the most coveted of big gamefish, and major recreational fisheries cater to the demand. A lot of resources are committed to the activity, particularly in the construction of private and charter billfishing boats to participate in the billfishing tournament circuit. These are expensive purpose-built offshore vessels with powerfully driven deep sea hulls. They are often built to luxury standards and equipped with many technologies to ease the life of the deep sea recreational fisherman, including outriggers, flying bridges and fighting chairs, and state of the art fishfinders and navigation electronics.

Most recreational fishermen now tag and release billfish.

As food

Billfish make good eating fish, and are high in omega-3 oils. Blue marlin has a particularly high oil content.

Mercury

However, because billfish have high trophic levels, near the top of the food web, they also contain significant levels of mercury and other toxins. According to the United States Food and Drug Administration, swordfish is one of four fishes, along with tilefish, shark, and king mackerel, that children and pregnant women should avoid due to high levels of methylmercury found in these fish and the consequent risk of mercury poisoning.

Conservation

Billfish are exploited both as food and as fish. Marlin and sailfish are eaten in many parts of the world, and many sport fisheries target these species. Swordfish are subject to particularly intense fisheries pressures, and although their survival is not threatened worldwide, they are now comparatively rare in many places where once they were abundant. The istiophorid billfishes (marlin and spearfish) also suffer from intense fishing pressures. High mortality levels occur when they are caught incidentally by longline fisheries targeting other fish. Overfishing continues to "push these declines further in some species". Because of these concerns about declining populations, sport fishermen and conservationists now work together to gather information on billfish stocks and implement programs such as catch and release, where fish are returned to the sea after they have been caught. However, the process of catching them can leave them too traumatised to recover.

The stocks for individual species in billfish longline fisheries can "boom and bust" in linked and compensatory ways. For example, the Atlantic catch of blue marlin declined in the 1960s. This was accompanied by an increase in sailfish catch. The sailfish catch then declined from the end of the 1970s to the end of the 1980s, compensated by an increase in swordfish catch. As a result, overall billfish catches remained fairly stable.

"Many of the world's fisheries operate in a data poor environment that precludes predictions about how different management actions will affect individual species and the ecosystem as a whole." In recently years pop-up satellite archival tags have been used to monitor billfish. The capability of these tags to recover useful data is improving, and their use should result in more accurate stock assessments. In 2011, a group of researchers claimed they have, for the first time, standardized all available data about scombrids and billfishes so it is in a form suitable for assessing threats to these species. The synthesis shows that those species which combine a long life with a high economic value, such as the Atlantic blue marlin and the white marlin, are generally threatened. The combination puts such species in "double jeopardy".

See also

  • Billfish in the Indian Ocean
  • The Old Man and the Sea

References

Further reading

  • Lynch PD, Graves JE and Latour RJ (2011) "Challenges in the assessment and management of highly migratory bycatch species: a case study of the Atlantic marlins" In: WA Taylor, AJ Lynch and M Schechter (Eds.), Sustainable Fisheries: Multi-level Approaches to a Global Problem, American Fisheries Society. . Review
  • Maguire, Jean-Jacques (2006) The state of world highly migratory, straddling and other high seas fishery resources and associated species Fisheries technical paper 495, FAO, Rome. .
  • Schultz, Ken (2011) Ken Schultz's Field Guide to Saltwater Fish John Wiley and Sons. .
  • Stobutzki I, Lawrence E, Bensley N and Norris W (2006) "Bycatch mitigation approaches in Australia's Eastern Tuna and Billfish Fishery: seabirds, turtles, marine mammals, sharks and non-target fish" Information Paper WCPFC-SC2/EBSWG–IP5. Ecosystem and Bycatch Specialist Working Group of the Second Meeting of the Scientific Committee of the WCPFC.
  • Ward P and Hindmarsh S (2006) "An overview of historical changes in the fishing gear and practices of pelagic longliners" WCPFC Scientific Committee, Second Regular Session.
  • Atlas of Tuna and Billfish Catches Interactive Atlas, FAO, Rome.
  • Family Istiophoridae at Fishbase.org
  • Family Xiphiidae at Fishbase.org
  • The Billfish Foundation
  • PBS/BBC/NHK Documentary Superfish
  • Bill Fish Outdoor Lodge.
  • One Quarter of Tuna and Billfish Fishstocks in Need of Conservation Fish Channel, 26 July 2011.
  • Swordfish & Billfish WWF.
  • Offield Center for Billfish Studies
  • Eastern Tuna And Billfish Fishery Management The FishSite, June 2011.
  • Billfish Tagging Tuna Research and Conservation Center.
  • Scientists find tuna and billfish species at risk European Commission, 12 September 2011.
  • One Quarter of Tuna and Billfish Fishstocks in Need of Conservation Fish Channel, 26 July 2011.
  • Blue marlin blues: Loss of dissolved oxygen in oceans squeezes billfish habitat EurekAlert, 14 December 2011.
  • Expanding Dead Zones Are Shrinking Tropical Blue Marlin Habitat ScienceDaily, 12 December 2011.
  • Study helps assess global status of tuna and billfish stocks EurekAlert, 15 August 2011.
  • Assessing Global Status of Tuna and Billfish Stocks ScienceDaily, 15 August 2011.
  • Campaign on mercury levels sparks controversy Tico Times, 20 May 2011.