NOAA Fisheries scientists in late June heralded the recovery of Pacific bluefin tuna as a major milestone, saying the species has exceeded international rebuilding targets a decade ahead of schedule.
In announcing the achievement on June 25, NOAA Fisheries credited international organizations across the Pacific with cooperating to reverse decades of overfishing for the prized species.
The International Scientific Committee (ISC) for Tuna and Tuna-Like Species in the North Pacific Ocean, including NOAA Fisheries researchers, provided expertise to inform the needed conservation measures. The Inter-American Tropical Tuna Commission (IATTC) and Western and Central Pacific Fisheries Commission (WCPFC) adopted the measures.
The new stock assessment was finalized recently by the International Scientific Committee at a meeting in Victoria, British Columbia. The assessment confirmed that the stock reached the second rebuilding target in 2021.
If current management measures persist, population growth is expected to continue.
“This is an amazingly resilient fish and the new assessment is showing us that. While the population is thriving, ongoing monitoring of data quality is essential to ensure the continued accuracy of the assessment,” said Huihua Lee, a research mathematical statistician at NOAA Fisheries’ Southwest Fisheries Science Center who led the work on the stock assessment in the United States.
“It also demonstrates the success of coordinated scientific efforts taken by the member countries through the ISC,” Lee added.
The stock assessments translate decades of high-quality data on Pacific bluefin and a thorough understanding of the biology of the species into accurate predictions of future trends, Lee said.
Pacific bluefin tuna are the largest species of tuna in the Pacific with adults reaching nearly 10 feet in length and 990 pounds. The habitat of this highly migratory species mostly spans the temperate waters of the North Pacific—from East Asia to the North American West Coast.
They are also among the fastest swimming species on the planet, living an average of 15 years.
Commercial vessels in the U.S. primarily land Pacific bluefin tuna using hook-and-line or purse seines. In 2022, U.S. commercial fishers harvested 368 metric tons of Pacific bluefin tuna, grossing more than $2.2 million in on-the-dock revenue, government data show.
The total U.S. fishing effort, both recreational and commercial, represented around 10% of total Pacific bluefin tuna landings that year. Japanese and Mexican vessels harvest the majority of the annual catch.
By the time that they’re harvested on the West Coast, Pacific bluefin tuna have already traversed the Pacific from their spawning grounds between central Japan and the northern Philippines and in the Sea of Japan. They arrive off the coast of Baja California, Mexico at around one year old.
They stay in the open waters off the U.S. and Mexico, feeding on squid, sardines, saury and herring, among other fish. At three to five years old, they migrate back to their spawning grounds—a nearly 6,000-mile journey that takes as little as 55 days for the speedy fish.
“Close collaborations between managers and scientists have been really key for the U.S. to develop a cohesive strategy to rebuild this pan-Pacific stock,” said Valerie Post, a fishery policy analyst with the NOAA Fisheries Pacific Islands Regional Office. “Everyone has played an important role in the science and management process, and our cumulative efforts have resulted in a success story for Pacific bluefin.”
Bluefin are assessed based on their unfished spawning stock biomass—the theoretical amount of fish there would be in the absence of fishing. Overfishing in the late 1990s and 2000s reduced the estimated bluefin biomass to a historic low of 2% of its potential unfished level from 2009–2012.
The decline prompted multi-lateral action beginning in 2011 to stem overfishing and rebuild the stock. The goal was to rebuild to at least 20% of the spawning stock biomass by 2034.
Pacific bluefin tuna are considered one stock throughout their range. The IATTC manages them in the eastern Pacific Ocean and the WCPFC manages them in the western and central Pacific Ocean. Both base their bluefin tuna management and conservation measures, which have been adopted by consensus, on science produced by the seven-country ISC.
The U.S. is a member of both commissions, and NOAA Fisheries leads American delegations and implements conservation and management measures agreed to by the groups.
Margaret Bauman margie@maritimepublishing.com