Environmental Initiatives

Media Inquiries

If you are a journalist and would like additional information, please visit the Media Contacts page.

Media Contacts

Subscribe to News Feeds

Pew offers news delivered to your desktop via RSS feed. Subscribing is easy. To learn more or get started, follow the link below.

Subscribe to News Feeds

For The Record

When Pew’s work is questioned or criticized we respond through letters to the editor or op-eds.

Read Pew's Responses

Improving the Count of Western Atlantic Bluefin Tuna

Fact Sheet

Additional Resources

How many wild bluefin tuna remain in the Atlantic Ocean?  How many can be removed from the ocean each year without jeopardising the future of the species? How much do the populations have to grow before we can proclaim them recovered and healthy? These are some of the key questions that governments must answer to ensure that their decisions about fishing bluefin tuna are responsible, and the fishery becomes sustainable. 

An accurate stock assessment is critical to achieving a well-managed, healthy Atlantic bluefin population. Of course, because bluefin tuna spend most of their lives swimming underwater in the open ocean, scientists can't count each individual fish. So, as with other fisheries, they have developed complex stock assessment models to estimate the number of bluefin tuna in the eastern and western Atlantic and to predict their population status into the future. Government managers rely on the results of these assessments, which are conducted every two to three years, to set fishing quotas.

In October 2012 the International Commission for the Conservation of Atlantic Tunas (ICCAT), the intergovernmental organization charged with managing Atlantic bluefin tuna, finalised the results of both the eastern and western Atlantic bluefin stock assessments. In the lead up to ICCAT’s annual meeting in November 2012, its member governments are currently in negotiations to determine new fishing quotas for 2013–2015 based on the assessment results and recommendations by ICCAT’s scientific committee (SCRS). 

The good news is that there is a growing body of science that is improving the understanding of bluefin biology and behavior and offering hope for a new and better stock assessment model.  ICCAT has recognised the need to incorporate this new science into its stock assessment. However, it is critical that, in line with scientific advice, Atlantic bluefin quotas do not increase until these assessments have been updated to reflect the best available science.  

Bluefin TunaMore Adults, More Young

ICCAT has set a target date of 2019 for rebuilding the western Atlantic bluefin population, a fish assessed as Endangered by the IUCN. To accurately predict the impact of management decisions on recovery levels and timelines, the SCRS needs to have a clear understanding of how many young each adult bluefin tuna can be expected to produce. While this may seem relatively straightforward, it has been a weak point of the western bluefin stock assessment for more than a decade.

The western population assessment currently uses two vastly different scenarios to model the adult-to-young ratio, or what fishery scientists refer to as the ‘stock-recruit relationship’ (SRR).  Under the ‘high recruitment’ scenario, it is assumed that the number of young will increase as the number of adults increases, and therefore a much higher catch level is possible in the future if the population is allowed to rebuild. Under the ‘low recruitment’ scenario, it is assumed that the number of adults does not influence the number of young produced, meaning that the fishery will never be much more productive than it is today as an increased number of adults is not expected to lead to increased young. These widely disparate models have led to a lack of clarity in management recommendations from SCRS scientists. Some years the SCRS has favored the low recruitment scenario, while in other years the high recruitment scenario has been used. At other times, including 2012, the SCRS presented the results of both the high and low recruitment scenarios to ICCAT governments for consideration.

Two recent scientific projects have taken a fresh look at the available data and been able to provide more specific guidance on the western Atlantic population's SRR. In June 2012, 13 of the world's leading bluefin scientists explored the consequences of using the high or low recruitment projections when forecasting the future trajectory of the bluefin population and presented these findings to the SCRS in September. Together they recommended that ICCAT employ ‘decision tables’, which compare the likelihood of success of different quota levels in achieving a specified goal (such as maximising the population size or catch in the short term or long term), under either the high or low recruitment scenarios. Such an approach allows fishery managers to consider more fully the longer term consequences of any decisions they make. In all scenarios, except the one aimed at maximising short-term catch, the high recruitment scenario-based decisions were the preferred management alternative.

Another study, by a scientist from the University of British Columbia, used sophisticated modeling techniques to determine whether historical counts of adults and young better support the high recruitment or low recruitment scenario. The results indicate that the high recruitment scenario is 4.8 times more likely than the low recruitment scenario, and strongly suggest a direct relationship between the number of adults and the number of young. This means that the population is probably able to increase to much higher levels than we see today.

Tuna Mixing 

For the last three decades, ICCAT has assessed and managed Atlantic bluefin tuna as if there are two distinct populations. Essentially drawing a line down the middle of the ocean at 45°W, ICCAT has assumed that there is an eastern population that spawns in the Mediterranean Sea and a western population that spawns in the Gulf of Mexico].  However, research conducted in recent years has revealed that bluefin behavior is not that simple. New studies – electronic tagging, genetics, and chemical analyses of bluefin tuna otoliths (earbones that can reveal the birthplace of individual tunas) – show that, while the two populations maintain separate breeding grounds, bluefin travel far in their search for food, and bluefin originating in the east mix extensively with western Atlantic bluefin in their feeding grounds in the North Atlantic. 

A new otolith study has shown just how extensive the mixing may be. Scientists at the University of Maryland and Texas A & M University determined that 72 percent of bluefin tuna caught off the coast of North Carolina and Virginia in 2011–2012 were born, not in the Gulf of Mexico as the current working hypothesis would assume, but in the Mediterranean Sea. In other words, the western Atlantic fishery is dependent on the immigration of Mediterranean-spawned eastern bluefin, which are then fished in western Atlantic waters. 

tuna-migration-776-RC.jpg

This study has significant implications for the western Atlantic bluefin stock assessment and management of the species. The large quantity of eastern fish in western waters is artificially inflating the count of western bluefin. Adding to the problem, persistent illegal fishing in the Mediterranean Sea is likely to be compromising the health and economic viability of the western fishery by removing eastern fish that would have migrated to the waters off North America. Recognising the inherent and insurmountable shortcomings of its current assessment models, ICCAT has acknowledged the need to update its stock assessment to incorporate the latest scientific knowledge about mixing.

Management Advice 

The 2012 stock assessment provides a glimmer of hope for western bluefin tuna, suggesting that the population has grown 13 percent since 2009. However, the population is still just 36 percent of what it was in 1970, a time when western bluefin had already been severely depleted by industrial fishing.  There is also concern that any population growth is more a reflection of increasing eastern migrants in western fisheries than an actual increased number of true western bluefin tuna.

As expected, the 2012 SCRS report to ICCAT included results for both the high and low recruitment scenarios. While the high recruitment scenario indicates that there is a 60 percent chance that overfishing can be stopped in the short-term by reducing quotas from 1,750 mt to 1,200 mt, it also indicates that the western Atlantic tuna population has no chance of rebuilding within the ICCAT deadline of 2019, even if the fishery is shut down. Under the low recruitment scenario, the report results show that quotas would need to be 2,000 mt or under to allow for an adult population that would be approximately the same size as it is today.

As the 2012 ICCAT annual meeting approaches, governments may be facing industry pressure to favor the low recruitment scenario and increase quotas in the western Atlantic in response to what the new stock assessment suggests is a barely discernible increase in the population. However, in their 2012 report, the SCRS scientists acknowledged the uncertainty in the current model and stated that maintaining the western quota at the current level of 1,750 mt will allow the bluefin tuna population to continue to increase, regardless of the relationship between the number of adults and the number of young they produce. The decision table approach, described above, was applied to the 2012 assessment results; after considering the likelihood of the two recruitment scenarios the scientists suggested that the quota should be maintained at 1,750 mt to maximise long-term catch and population size.

The next step is clear. When ICCAT governments convene in Agadir, Morocco in November 2012, it is imperative that they heed the scientific advice and not increase the western Atlantic bluefin tuna quota beyond 1,750 mt for at least the next three years or until the stock assessment model has been modernised and updated to reflect current scientific knowledge. Since the stock assessment erroneously counted a large number of ‘eastern’ bluefin as ‘western’ bluefin, any decision to increase quotas would not only be misguided but would be likely to lead to further declines in the severely depleted western population.

Fact Sheet File: Improving the Count of Bluefin (PDF)

 

Related News and Resources

  • Protecting the High Seas From Peril

    • Other Resource
    • Apr 01, 2014
    All the activity in the open ocean raises questions about who is monitoring and managing the ocean’s long-term health. As of now, the job is vacant, which is why delegates from around the world are at the United Nations in New York City this week.

    More

  • Climate Change Taking Toll on the Ocean

    • Other Resource
    • Mar 31, 2014
    A United Nations panel released its latest assessment of the impact of climate change on the world’s environment, focusing on issues such as food supply and economic security.

    More

  • Pew Comments on Amendment 28 to the Reef Fish Fishery Management Plan

    • Other Resource
    • Mar 25, 2014
    On March 25, 2014, Chad W. Hanson of The Pew Charitable Trusts wrote a letter to Doug Boyd, Chairman of the Gulf of Mexico Fishery Management Council, regarding Amendment 28 to the Reef Fish Fishery Management Plan [Red Snapper Allocation].

    More

  • Pew le otorga al científico Hoyt Peckham la beca de investigación 2014 en conservación de recursos marinos

    • Press Release
    • Mar 12, 2014
    El Dr. Hoyt Peckham, un pionero en la incentivación de la pesca artesanal para promover el manejo de los recursos marinos con sede en La Paz, México, ha recibido una beca de investigación Pew 2014 en la conservación de dichos recursos marinos para ampliar su trabajo en la incentivación de la pesca sostenible a lo largo de la costa del noroeste de México a otras comunidades de la región y a nivel mundial. Peckham está trabajando con los pescadores locales y sus cooperativas para restablecer el valor de sus pesquerías, reforzando sus prácticas de sostenibilidad mediante el aumento de la demanda de sus mariscos y sus pescados.

    More

  • Pew Awards Author Paul Greenberg the 2014 Fellowship in Marine Conservation

    • Press Release
    • Mar 12, 2014
    Paul Greenberg—an award-winning journalist and author of the New York Times bestseller, Four Fish: The Future of the Last Wild Food—has been awarded a 2014 Pew fellowship in marine conservation to prepare a book focusing on the human demand for Omega 3 fatty acids found in seafood and its impact on the sustainability of the world’s oceans.

    More

  • Pew le otorga al científico chileno Stefan Gelcich la beca de investigación 2014 en conservación de recursos marinos

    • Press Release
    • Mar 12, 2014
    Se ha reconocido al Dr. Stefan Gelcich, profesor adjunto de la Pontifica Universidad Católica de Chile con una beca de investigación Pew 2014 para la conservación de recursos marinos en un nuevo proyecto que examinará los incentivos sociales, económicos y ecológicos que permitan desarrollar zonas de protección, en conjunto con pescadores artesanales, a lo largo de la costa chilena. Este científico estudiará la integración de áreas marinas protegidas y pesquerías con derechos de uso territorial, como una estrategia para la conservación a largo plazo de los recursos oceánicos y su sostenibilidad.

    More

  • Pew Awards Shark Scientist Demian Chapman the 2014 Fellowship in Marine Conservation

    • Press Release
    • Mar 12, 2014
    Demian Chapman, Ph.D., a scientist with Stony Brook University’s School of Marine and Atmospheric Science, has been awarded a 2014 Pew fellowship in marine conservation for a new research project to determine how recently enacted international regulations affect the trade in the fins of protected shark species. Sharks have been heavily fished to supply the international fin trade, depriving marine ecosystems of some of their most important top predators and endangering species dependent on them.

    More

  • Pew Awards Malaysian Mammal Scientist the 2014 Fellowship in Marine Conservation

    • Press Release
    • Mar 12, 2014
    Louisa Shobhini Ponnampalam, Ph.D., a scientist with the University of Malaya in Kuala Lumpur, Malaysia, and co-founder of grassroots NGO, The MareCet Research Organization, has been awarded a 2014 Pew Fellowship in Marine Conservation to conduct new research on the country’s population of dugongs, a large coastal marine mammal that resembles the manatee.

    More

  • Pew on the Road: Visiting Fishing Communities in the Southeast

    • Other Resource
    • Mar 07, 2014
    In just the past two months, Pew staff hit the road to talk with commercial fishermen and their families at a seafood festival, meet with anglers at a boat show, learn about the latest developments in marine science at a fisheries science conference, and film important underwater locations in the U.S. Caribbean.

    More

  • Speak Up for Emperor Penguins

    • Other Resource
    • Mar 03, 2014
    The emperor penguin colony made famous in the Academy Award-winning documentary “March of the Penguins” faces extinction because of climate change.

    More

  • Save the Boreal, Save the Caribou

    • Other Resource
    • Mar 03, 2014
    For millennia, the people who live in the far reaches of North America’s boreal forest have relied on woodland caribou for their survival. Now, the tables have turned.

    More

  • Engineering Pacific Bluefin's Comeback

    • Other Resource
    • Mar 03, 2014
    Pacific bluefin could make a relatively quick comeback from unsustainable fishing practices. They just need a bit of practical help.

    More

  • Dispatch From Fiji: Putting New Shark Protections to Work

    • Other Resource
    • Feb 27, 2014
    The listings in Appendix II of CITES for porbeagle sharks, oceanic whitetip sharks, three species of hammerhead sharks, and two species of manta rays mandate that all international trade in these species must be legal and sustainable.

    More

  • Oregon: One Last Piece of the Puzzle

    • Other Resource
    • Feb 24, 2014
    California and Washington conserve forage fish in state waters for the sake of the ecosystem. Action by Oregon state leaders is the last piece of the puzzle.

    More

  • Technology for Fisheries Monitoring and Surveillance

    • Other Resource
    • Feb 20, 2014
    Monitoring and surveillance of fisheries is a complex and challenging problem. Traditionally, ships and aircraft have been the mainstay of surveillance efforts, however, the use of satellites and other technologies by fisheries enforcement officials has increased in recent years.

    More

See more...

X
Sign In

Member Sign In

Forgot Password?
Submit Not a Member? Join!
X

Forgot Password?

Send Password Not a Member? Join!
X

Change Password

X
(All Fields are required)
Send Message
Share this on: