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HONOLULU (NOAA) – The recovery of Pacific bluefin tuna has reached a significant milestone – the species’ recovery has surpassed international targets a decade ahead of schedule.
The recovery of Pacific bluefin tuna reflects a successful fishery management effort, with international organizations on both sides of the Pacific working together to reverse decades of overfishing of this valuable species.
The International Scientific Committee (ISC) on North Pacific Tuna and Bluefin Tuna Species, including NOAA Fisheries researchers, provided scientific expertise to guide the conservation measures, which were adopted by the Inter-American Tropical Tuna Commission (IATTC) and the Western and Central Pacific Fisheries Commission (WCPFC).
The ISC recently completed a new stock assessment at its annual meeting in Victoria, Canada. The assessment confirmed that the population reached its second rebuilding goal in 2021. If current management measures continue, population growth is expected to continue.
“This is an incredibly resilient fish, and the new assessment shows us that. While populations are thriving, continued monitoring of data quality is critical to ensure the continued accuracy of the assessments,” said Dr. Huihua Li, a research mathematical statistician at NOAA Fisheries’ Southwest Fisheries Science Center, who leads the U.S. stock assessment effort.
“It also demonstrates the success of member states’ coordinated scientific efforts through the ISC.”
Dr. Lee said the stock assessment translated decades of high-quality data on Pacific bluefin tuna and a thorough understanding of the species’ biology into accurate predictions of future trends.
The Pacific bluefin tuna is the largest tuna species in the Pacific Ocean, with adults reaching nearly 10 feet in length and weighing 990 pounds. This highly migratory species is found primarily in the temperate waters of the North Pacific Ocean—from East Asia to the west coast of North America. They are also one of the fastest swimming species on Earth, with an average lifespan of 15 years.
In the United States, recreational and commercial vessels primarily fish for Pacific bluefin tuna using hook and line or purse seine nets. In 2022, U.S. commercial fishermen caught 368 metric tons of Pacific bluefin tuna, grossing more than $2.2 million at the dock.
That year, U.S. recreational and commercial fishing combined accounted for about 10 percent of the Pacific bluefin tuna catch. Japanese and Mexican vessels took the bulk of the annual catch.
By the time Pacific bluefin tuna are caught on the West Coast, they have already crossed the Pacific Ocean from spawning grounds in central Japan and the northern Philippines and the Sea of Japan. They reach the coast of Baja California, Mexico, when they are about a year old. They inhabit open waters in the United States and Mexico, feeding on fish such as squid, sardines, saury and herring. They migrate back to their spawning grounds when they are 3 to 5 years old – a journey of nearly 6,000 miles in just 55 days for this speedy fish.
While successful management of bluefin tuna requires significant international cooperation, it also requires coordination within NOAA Fisheries. The Southwest Fisheries Science Center provides scientific analysis for ISC’s stock assessments.
The West Coast and Pacific Islands regional offices collaborate on domestic and international inventory management.
“Close collaboration between managers and scientists is critical to the U.S. developing a unified strategy to restore pan-Pacific fish stocks,” said Valerie Post, fisheries policy analyst for NOAA’s Pacific Islands Regional Fisheries Service. “Each person plays an important role in the science and management process, and our combined efforts have resulted in successful conservation efforts for Pacific bluefin tuna.”
Assessments of bluefin tuna are based on their unfished spawning biomass – the theoretical number of fish that would be present if no fishing took place. Overfishing in the late 1990s and early 2000s reduced the estimated biomass of bluefin tuna to an all-time low of 2% of the potential unfished level in 2009-2012. This alarming decline prompted a multilateral effort to curb overfishing and restore bluefin tuna stocks in 2011. The goal is to restore spawning biomass to at least 20% by 2034.
Pacific bluefin tuna is considered a single stock throughout its range. The Inter-American Tuna Commission manages bluefin tuna in the Eastern Pacific, and the Western and Central Pacific Fisheries Commission manages bluefin tuna in the Western and Central Pacific. The management and conservation measures for bluefin tuna in both commissions are based on the scientific conclusions of the seven-nation ISC and are adopted by consensus. The United States is a member of both commissions. NOAA Fisheries leads the U.S. delegation and implements the conservation and management measures agreed upon by the two organizations.
In 2011, WCPFC members agreed to begin managing to recover the stock by reducing catches of both juvenile and older fish. This gave more fish a chance to grow up and reproduce. The following year, IATTC implemented conservation measures to reduce catches in its management areas. The two committees continue to coordinate across the Pacific, using the best available science to inform management decisions across the species’ range.
Although numbers were beginning to increase, in 2016 NOAA Fisheries received a petition to list Pacific bluefin tuna as threatened or endangered under the Endangered Species Act. A status review team conducted a 12-month review. They determined that while numbers were near historic lows, about 1.6 million fish were enough to avoid the risk of extinction. Management changes effectively addressed overfishing concerns.
However, the pace of recovery has been much faster than expected. Because each female Pacific bluefin tuna lays millions of eggs per batch, Pacific bluefin tuna have a natural ability to recover when international coordinated efforts reduce fishing pressure. The most recent stock assessment shows that the number of spawning bluefin tuna reached 23.2% of the potential unfished spawning stock in 2022. This milestone marks the first time that the stock has exceeded the maximum sustainable yield level associated with the species. The rapid recovery of the Pacific bluefin tuna population suggests that production may increase in the coming years as the population continues to grow.
“You have to find a balance between having a good harvest and having a permanent increase in fish stocks, and we’ve crossed that balance,” said Celia Barroso, a fisheries policy analyst for the West Coast region of NOAA Fisheries.
The IATMC and WCPFC joint Northern Commission bluefin tuna management working group will meet in Japan in July to make recommendations on conservation and management measures for 2025 and beyond. IATMC and WCPFC must adopt the recommendations at their annual meetings later this year.
The next step in international bluefin tuna management is to develop a long-term harvest strategy starting next year. Researchers at the Southwest Fisheries Science Center will help lead a management strategy review. It will engage the fishery, managers, scientists and environmental groups to inform the new harvest strategy.
“The recovery of Pacific bluefin tuna shows what can be accomplished when scientists, managers and the fishing community work together on the international stage toward a common goal,” said Ryan Wolfe, assistant administrator for the West Coast region of NOAA Fisheries and acting U.S. commissioner of the Inter-American Tuna Commission.
“We will continue to work hard to ensure sustainable fishing of bluefin tuna for decades to come,” he said… PACNEWS
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