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How do you protect a fish that crisscrosses oceans?

It Really Sucks Being a Tuna

The fishers of Pohnpei Island use the feeding patterns of seabirds to spot tuna. Commercial tuna fishers use a modern version of this method - helicopters. Overfishing is putting some tuna populations at risk of collapse. Saving these fish is made more difficult by the great distances these fish swim and the high price they fetch.

 The price of fish

Depending on the species, a single tuna can sell for thousands of dollars. This creates a lot of incentive to catch as many tuna as possible. But this approach results in overfishing.

As tuna populations drop, their value increases, and it becomes even more lucrative to catch as many tuna as you can. Some species of tuna are now so valuable that it is economic to use helicopters and other expensive methods to catch them and bring them freash to market.

Some tuna populations have dropped by 90% since the 1950’s, and unless we preserve their numbers there will be no tuna left to catch.

 Preserving tuna (without a can)

One successful method for preserving fish numbers is to set aside areas as no fishing zones, called marine protected areas or marine reserves. With no fishing, fish numbers increase and they spill out of the MPA into areas where they can be fished.

But how do you protect a migratory species that can cross-cross the ocean several times throughout its life?

The answer may be to protect areas where tuna congregate, like migratory routes or spawning grounds. Traditionally, these areas have been used to catch a lot of fish with very little effort.  If these areas are protected instead, tuna may have a better chance to rebuild their numbers and give us a continuous supply of food.

 Tuna and sustainability

Fishing is a type of disturbance. Ecosystems can adapt to, and sometimes even benefit from disturbance, but like all types of disturbance, too much fishing lowers diversity and productivity. To ensure that we have a continued supply of tuna we need to fish these animals at a sustainable rate.

 References

Gillett, R. et al. (2001, March). Tuna: A key economic resource in the Pacific Islands. Asian development bank. PDF retrieved 25 August 2008 from http://www.adb.org/Documents/Reports/Tuna/tuna.pdf

Harui, R. (2008, January 5). Hong Kong Sushi Shop Pays Record Price for Tuna, AFP Reports. Bloomberg.com. Retrieved 26 August 2008 from http://www.bloomberg.com/apps/news?pid=20601080&sid=aeNM91VklNMo&refer=asia

ICRN. (2006, November 1). ICRI statement on Coral Reef Fish Spawning Aggregations. International coral reef initiative. PDF retrieved 25 August 2008 from http://www.env.go.jp/nature/biodic/coralreefs/icri/pdfs/assembly/cozmelGM/statements/State_CR_Fish_Spawning_aggregations2006.pdf

Langley, A. et al. ().The western and central pacific tuna fishery: 2006 overview and status of tuna stocks. Secretariat of the Pacific Community. Retrieved 21 August 2008 from http://www.spc.int/oceanfish/Docs/Research/wcptf.htm

Murphy, B. (2005, July 28). A Tale of Two Oceans: The Demise of Bluefin Tuna. Department of Fisheries & Wildlife Sciences. PDF retrieved 21 August 2008 from http://seminar.mannlib.cornell.edu/topicsfisheries/case_study.pdf

Myers, R. & Worm, B. (2003). Rapid worldwide depletion of predatory fish communities. Nature. PDF retrieved 21 August 2008 from http://www.fisherieswatch.org/docs/261.pdf

Sea Web. (2004, December 23). Offshore Fisheries in the Pacific Islands. Sea Web. PDF retrieved 21 August 2008 from http://www.seaweb.org/programs/asiapacific/documents/Offshore.pdf

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