May 12, 2010

Pacific bluefin tuna stocks decline

Similar to the one suffered by the Atlantic bluefin tuna, large-sized Pacific bluefin tuna populations with reproductive capacity are diminishing at a fast rate, says a recent Japanese study.

The study's findings point to the need to hasten efforts to restrict Atlantic and Pacific bluefin tuna catches for the protection of resources. Both of these species are consumed in immense quantities in Japan.
   

The study was led by Toshio Katsukawa, an associate professor and expert on marine resources at Mie University, whose research showed that the overexploitation of large-sized fish has resulted in an increase in the catch of juvenile small fish younger than three years or before egg production.
   

''It is imperative to suspend the catch during egg production periods and reduce the capture of juvenile fish. If we wait to catch them until they get bigger, the resources will recover and the revenue of fishermen will also increase,'' Katsukawa highlighted.

   
Japan catches more than 70% of the bluefin tuna fished in the Pacific Ocean, and 55% of that amount is caught with encircling nets. It has also become popular to catch young fish and breed them in recent years.
   

The average weight of bluefin tuna today is around 50 kilogramme against the average of 100-160 kilogramme in the 1980s, according to estimates by Katsukawa based on the amount of fish caught with encircling nets and the amount traded at Tokyo's Tsukiji fish market.

       
The average annual value of tuna aged less than two years was JPY2.7 billion (US$29 million) on landing ports between 2004-08.

   
But according to the study, if the young fish are not caught until they reach seven years old, their average value will rocket to JPY223.5 billion (US$2.4 billion).

   
Japan caught about 17,800 tonnes of Pacific bluefin tuna and imported about 3,800 tonnes in 2008, almost as much as the amount of Atlantic bluefin consumed in Japan yearly.