Pacific Bluefin Stocks in Jeopardy

The International Scientific Committee for Tuna and Tuna-Like Species in the North Pacific Ocean (ISC) reports that Pacific bluefin tuna (Thunnus orientalis) stock abundance is precariously low.  Pacific bluefin constitute a single Pacific wide stock with spawning occurring only in the western North Pacific Ocean.  Some proportion of the stock undertakes long migrations from the eastern North Pacific Ocean to Mexico and southern California, where they may reside for several years before migrating west again to spawn.  Spawning takes place around age three and Pacific bluefin may live as long as 20 years.

By the early 1950s, Pacific bluefin tuna were being targeted intensively by commercial fishers and landings peaked at 40,383 mt in 1956 followed by a low of 8,653 in 1990.  This species is harvested primarily with purse seine gear and juveniles have historically composed most (90%) of the catch, but the catch of age zero fish increased markedly since the early 1990s.  Put another way, much of the fish that are being caught weigh as little as one kilogram and have never had a chance to spawn.  As a result, stock biomass is thought to have declined by over 94% and scientists believe that the spawning stock may be comprised by a single year class that may be reaching the end of their natural life span. 

Scientists are recommending up to a 50% reduction in harvest of juvenile bluefin in the western Pacific and a 50% reduction in total harvest of bluefin in the eastern Pacific.  Recent science also indicates that establishing a minimum size of 20 kilograms could increase spawning stock size by as much as 400% in five years.   

In order to rebuild the Pacific bluefin tuna stock to sustainable levels it is imperative that fisheries managers heed the advice of scientists and that recreational and commercial anglers alike adhere to any new regulations that are put forth.

Western and Central Pacific Fisheries Commission: Preliminary Analyses of the Potential Impacts of Minimum Weight Regulations for Pacific Bluefin Tuna