Biodiversity: Tuna populations verging on collapse

A rampant black market and lax regulations are quickly leading to the demise of the eastern Atlantic bluefin tuna.

Drastic reductions in catch needed to recover populations

By Summit Voice

SUMMIT COUNTY — You may want to think twice before you order your next plate of sushi. Five of eight tuna species have been assigned threatened or near-threatened status on the international Red List maintained by the International Union for the Conservation of Nature.

The listing comes as the IUCN completes an assessment of all species of scombrids (tunas, bonitos, mackerels and Spanish mackerels) and billfishes (swordfish and marlins). Of the 61 known species, seven are classified in a threatened category, being at serious risk of extinction. Four species are listed as near threatened, while nearly two-thirds have been placed in the least concern category.

The only way to recover tuna populations before they collapse completely is to drastically reduce fishing and to enforce those regulations, a group of international researchers said in a strongly worded warning.

“This is the first time that fishery scientists, ichthyologists and conservationists have come together to jointly produce an assessment of the threats facing a commercially important group of fishes,” said Dr. Bruce B. Collette,  senior scientist with the U.S National Marine Fisheries Service, and lead author of the paper.

The results are particularly serious for tunas. Five of the eight species of tuna are in the threatened or near-threatened IUCN Red List categories, including southern bluefin (Thunnus maccoyii), critically endangered; Atlantic bluefin (T. thynnus), endangered; bigeye (T. obesus), vulnerable; yellowfin (T. albacares), near threatened; and albacore (T. alalunga), near threatened.

This new information will help governments make decisions to safeguard the future of these species, many of which are of extremely high economic value, and is a timely input for the 3rd Joint Meeting of the tuna regional fisheries management organizations) in La Jolla, California, July 11-15.

The biggest challenge may be a flourishing illegal trade in tuna. An investigation last year by the International Consortium of Investigative Journalists showed the eastern Atlantic bluefin tuna population is being decimated by a $4 billion black market, rampant fraud and lack of oversight and enforcement.

According to the report, Mediterranean fishermen have been violating quotas at will and have engaged in numerous illegal fishing practices, including misreporting catch size, hiring banned spotter planes, catching undersized fish, and trading fishing quotas.

There is growing concern that in spite of the healthy status of several epipelagic fish stocks (those living near the surface), some scombrid and billfish species are being heavily overfished, and there is a lack of resolve to protect against overexploitation driven by high prices. Many populations are exploited by multinational fisheries whose regulation, from a political perspective, is exceedingly difficult.

“All three bluefin tuna species are susceptible to collapse under continued excessive fishing pressure. The southern Bluefin has already essentially crashed, with little hope of recovery,” said co-author Dr. Kent Carpenter, Professor at Old Dominion University and manager of IUCN’s Marine Biodiversity. “If no changes are made to current fishing practices, the western Atlantic Bluefin stocks are at risk of collapse as they are showing little sign that the population is rebuilding following a significant reduction in the 1970s.”

Three species of billfishes are in threatened or Near Threatened categories: Blue Marlin (Makaira nigricans), Vulnerable; White Marlin (Kajikia albida), Vulnerable; and Striped Marlin (Kajikia audax), Near Threatened.

Most of the long-lived economically valuable species are considered threatened. They mature later than short-lived species and their reproductive turnover is longer, and as such recovery from population declines takes more time. As these scombrids and billfishes are at the top of the pelagic food web, population reductions of these predators may cause significant negative effects on other species that are critical to the balance of the marine ecosystem and that are economically important as a source of food.

The future of threatened scombrids and billfishes rests on the ability of RFMOs and fishing nations to properly manage these species. Southern and Atlantic Bluefin populations have been so reduced that the most efficient way to avoid collapse is to shut down the fisheries until stocks are rebuilt to healthy levels. However, this would cause substantial economic hardship and hinder the ability of RFMOs to control fishing because of the increased incentive for illegal fishing that would be created under these circumstances.

“Temporarily shutting down tuna fisheries would only be a part of a much needed recovery programme. In order to prevent illegal fishing, strong deterrents need to be implemented,” said Jean-Christophe Vié, deputy director of IUCN’s Global Species Programme. “This new study shows that there is an urgent need for effective management. Scientific findings should not be discarded in order to maintain short-term profit. Marine life and jobs for future generations are both at stake.”

The recovery of fish stocks is possible through reducing fishing-induced mortality rates to well below the maximum sustainable yield, as shown in the case of the highly valued eastern population of the Atlantic Bluefin. Recently exploited at three times the maximum sustainable yield, a decrease in the total allowable catch and stricter monitoring and compliance measures have led to recent catch reductions of almost 75 percent during the past few years. This will enable the species to recover to sustainable levels as long as the current fishing controls are maintained.


The tuna and billfish assessments are a part of the Global Marine Species Assessment’s mission to complete more than 20,000 marine species assessments for inclusion on the IUCN Red List of Threatened Species. The Global Marine Species Assessment Unit (GMSA), or Marine Biodiversity Unit, is a joint initiative of IUCN and Conservation International. The GMSA is headquartered in the Department of Biology at Old Dominion University in Norfolk, Virginia, and is largely enabled by the generous support of the New Hampshire Charitable Foundation and Tom Haas.

To complete the tuna and billfish IUCN Red List assessments, the GMSA collaborated with a wide diversity of international scientists who represent Fisheries Management Organizations, international conservation organizations; government agencies, universities, and independent fisheries research institutions.

Complete results of the tuna and billfish species assessments will be published on the IUCN Red List of Threatened Species in November 2011. As of July 7, 2011, draft assessments are online at:


4 thoughts on “Biodiversity: Tuna populations verging on collapse

  1. As a sushi lover, I would be happy to do away with tuna because there are a lot of other veggie and sustainable sushi I can eat and I would like other sushi lovers to give tuna a break.

  2. Easy enough to avoid blue fin & yellowtail in the sushi restaurants as patrons, more challenging to hold the restaurants accountable by asking that tuna be removed from the menu.
    I seem to recall a similar situation a few years back regarding swordfish and restaurants in Aspen.

    Also, albacore was mentioned which is found in supermarkets labeled as “solid white”. Again, easy enough to avoid. What species is in canned tuna labeled “chunk light”, and does that need to be avoided as well?

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