The decline of Atlantic bluefin tuna is the quintessential example of human overexploitation at sea. In this blog post, I hope to not only identify major threats to this species but examine the historical roots of these threats.


Historically, humans have fished tuna sustainably for centuries: a feat which can primarily be attributed to the relatively low demand and value placed on bluefin tuna. Tuna were initially caught along the Atlantic coast mainly for sport as opposed to consumption. At the very height of tuna sport fishing during the mid-1900s, bluefin tuna still sold for only a few pennies a pound in the United States, and carcasses were often ground into cat food, sent to landfills, or dumped back into the sea (Corson 2008). Even as a food product in Japan, bluefin tuna was unpopular due to the unusually red, smelly, and bloody qualities of the meat, which differed greatly from the mild tasting fish typically consumed by the Japanese at the time, mainly white fish and shellfish (Corson 2008).

After World War II, a drastic shift occurred in the popularity of tuna as advanced refrigeration technology prevented smelly, red-fleshed fish from spoiling and the Japanese began to acquire a taste for rich, fatty red meat, such as beef, from Americans. This resulted in an increased demand for bluefin tuna that also happened to coincide with a period of massive globalization. Japanese planes delivering electronics to the United States began to capitalize on cheap bluefin tuna available in New England to fill up their empty planes on the flight back home, where the tuna was then sold for thousands of dollars. As the popularity of bluefin tuna skyrocketed in the Japanese sushi market, trends in American sushi soon began to follow suit, and by the 1990s, the bluefin tuna was in high demand worldwide (Corson 2008).

Today, sushi is a multibillion dollar industry, and bluefin tuna has grown to have immense market value in the global economy, particularly in Japan. In fact, between 1970 and 1990, fishing for bluefin tuna in the Western Atlantic rose by over 2,000%, while the average price paid to Atlantic fishermen for bluefin exported to Japan increased by 10,000%. One extravagant demonstration of the increasing value of bluefin tuna occurred in 2013, when an owner of a Japanese sushi restaurant chain paid a record $1,763,000 for the first bluefin tuna sold at the renowned Tsukiji fish market in Tokyo (Associated Press 2013).

Unfortunately, the high monetary value in tandem with the increasing rarity of the bluefin tuna has created an anthropogenic allee effect, where the smaller the population of bluefin, the more valuable the rare tuna becomes and the more heavily exploited they are by humans. With Japan consuming approximately 75-80% of the worlds’ catch of bluefin tuna, some major Japanese corporations are prepared to take advantage of this effect (Hamilton et al. 2011). For example, Mitsubishi, a company which handles 35-40% of Japan’s imported Atlantic bluefin tuna, has been deep-freezing and stockpiling thousands of tons of bluefin each year, seeking to profit by selling bluefin at extremely steep prices in the future when the bluefin tuna is extinct or near extinction. With declining populations only accelerating the process of extinction, Atlantic bluefin tuna are a species at significantly high risk.

Major Threats

Overfishing is the single biggest threat to Atlantic bluefin tuna today. The story of human overexploitation of Atlantic bluefin tuna exemplifies a pivotal moment in marine history. After World War II, there was not only a surge of globalization leading to the high demand for bluefin, but also a surge in new war technology that was redirected towards fishing efforts, ultimately leading to a massive expansion and intensification of global fishing (Blackford 2008). Fishing fleets began incorporating sonar and radar to detect fish schools, while special buoys, or fish aggregating devices, were used to attract pelagic fish like bluefin tuna. At-sea freezing technology was also developed, allowing vessels to stay out at sea for longer periods of time and expand their fishing territory. Giant nets called purse seines were introduced to enclose and scoop up entire schools of fish from large sections of the ocean. These purse seines quickly became the most common gear used in the Mediterranean, leading to the emergence of a technologically advanced fleet of purse seining vessels. Despite scientific evidence of overfishing and depleted bluefin tuna stocks, during the period of 2005-2007 alone, the European purse seine fleet doubled in size as more vessels were employed to hunt down dwindling bluefin populations, with subsidies continuing to sustain the EU fishing industry at a rate of more than €800 million per year (Willson 2012). What resulted from these technological advancements in fishing was a new era of industrial scale, commercial exploitation of the sea.

However, not even advanced fishing technology could satiate demand for bluefin, resulting in the boom in illegal, unreported, and unregulated (IUU) fishing. Underneath the surface of the bluefin industry lies a massive black market conservatively valued at $4 billion (Guevara et al. 2010). At its peak between 1998 and 2007, more than 1 in 3 bluefin was caught illegally (Guevara et al. 2010). Illegal practices occur throughout the bluefin industry from fishing vessels and farms to distributors in Japan all the way up to government officials. For example, fishing vessels would illegally catch undersized tuna and hire banned spotter planes to locate schools of tuna from the air (Guevara et al. 2010). Vessels and ranches would deliberately underreport catch data and a market even emerged around trading quotas, where one vessel sells it’s nation’s quota to a foreign vessel that has overfished (Guevara et al. 2010). Giant cargo vessels, or reefers, also pose a significant problem, in addition to ranches, as a means of sneaking in illegal tuna. With a length of over 100 meters, reefers essentially act as floating freezers to store tuna caught by various fishing vessels (Chartier 2013). Reefers have become the perfect loophole to sneak in illegally sourced fish through transshipping, the practice of transferring fish catches from one vessel to another, which often occurs outside of regulated exclusive economic zones (Chartier 2013). As catches are transferred from boat to boat and then aggregated on a single reefer, it becomes increasingly difficult to determine which vessel caught which fish and where.

ICCAT Corruption and Controversy

The primary governing body in charge of Atlantic bluefin tuna is the International Commission for the Conservation of Atlantic Tunas (ICCAT). ICCAT was formed in 1966 to manage the conservation of tunas and tuna-like species in the Atlantic Ocean and adjacent seas (ICCAT 2007). In theory, ICCAT sets yearly total allowable catch limits based on scientific advice provided in stock assessments conducted approximately every two years by their Standing Committee on Research and Statistics (SCRS). However, ICCAT has been infamous for implementing poor management practices, instead referred to by other conservationists as “an international disgrace” and the “International Conspiracy To Catch All Tuna” (Brower 2014).

One of the biggest controversies surrounding ICCAT occurred in 2008 when scientists recommended a total allowable catch of 15,000 mt to maintain the current eastern Atlantic bluefin tuna population and 10,000 mt to work towards population recovery (ICCAT 2009). However, ICCAT decided to set a quota of 28,500 mt with actual catch estimated to be 61,000 mt, or 1/3 of remaining stocks, when accounting for IUU fishing (ICCAT 2009).

Ultimately, the plight of the Atlantic bluefin tuna serves as a significant case study for examining the human relationship with the ocean and revealing a history of overexploitation that extends to marine species beyond bluefin.


Associated Press. 2013. Bluefin tuna sells for record $1.76M in Tokyo., Manila, Philippines. Available from (accessed December 2017).

Blackford, Mansel. 2008. A Tale of Two Fisheries: Fishing and Over-Fishing in American Waters. Origins: Current Events in Historical Perspective 1:92-106

Brower, K. 2014. Quicksilver. National Geographic, Washington, D.C. Available from (accessed December 2017).

Chartier, François. 2013. Floating freezers full of tuna, but where did it come from? Greenpeace France, Paris, France. Available from (accessed December 2017).

Corson, Trevor. 2008. The Story of Sushi: An Unlikely Saga of Raw Fish and Rice. Pages 1-416. Harper Perennial, New York City, New York.

Guevara, M. W., Willson, K., Garcia Rey, M. 2010. Overview: The black market in bluefin. The Center for Public Integrity, Washington, D.C.

Hamilton, A., Lewis, A., McCoy, A. M., Havice, E., Campling, L. 2011. Market and Industry Dynamics in the Global Tuna Supply Chain. Pacific Islands Forum Fisheries Agency.

International Commission for the Conservation of Atlantic Tunas (ICCAT). 2007. Introduction. ICCAT, Madrid, Spain. Available from (accessed December 2017).

ICCAT. 2009. Report of the 2008 bluefin tuna stock assessment session. Report of the biennial period 2008-09. International Commission for the Conservation of Atlantic Tunas.

Willson, K., and Canet, J. 2012. A Mediterranean feeding frenzy. International Consortium of Investigative Journalists, Washington, D.C.Worm, B., and Tittensor, D.P. 2011. Range contraction in large pelagic predators. proceedings of the National Academy of Sciences 108:11942-11947.