- During its annual meeting this month, the Indian Ocean Tuna Commission (IOTC) reframed management measures for yellowfin tuna following a determination that the species’ stock health has improved.
- Industry representatives welcomed the decision, but conservationists are urging caution, citing the long history of yellowfin overfishing and the difficulties in monitoring and curbing overexploitation.
- The IOTC also moved on regulating the swordfish fishery in the Indian Ocean by determining enforceable catch limits for members.
- Manta and devil rays are especially at risk in tuna fisheries; the IOTC adopted guidelines for their handling and release to reduce bycatch mortality.
An annual meeting of the regulatory body overseeing the tuna fishery across the Indian Ocean has agreed to update the rules governing one of the region’s most iconic species: yellowfin tuna.
The easing of fishing curbs can be traced to the Indian Ocean Tuna Commission’s (IOTC) scientific body finding that Thunnus albacares stocks aren’t overfished, nor are they currently experiencing overfishing in the Indian Ocean. The body first made the determination in 2024, but the finding underwent an internal review process before being accepted by the commission at its recent meeting in the Maldives. The meeting held in May was attended by delegates from coastal nations in Asia, Africa and Oceania, as well as distant-water fishing powers like Japan and the European Union.
Now, that scientific advice has translated into a reframing of the management rules, provoking sharply divided reactions. Conservationists are urging caution, citing the long history of yellowfin overfishing and the difficulties in monitoring and curbing overexploitation. Industry representatives, meanwhile, hailed the decision, saying it secures access to one of the region’s most lucrative tuna fisheries.
At the meeting in the Maldives, parties agreed on a total allowable catch (TAC) and quotas for contracting members for the period from 2027-2028. In doing so, the IOTC became the first tuna regional fisheries management organization (RFMO) to implement catch allocation systems for all three tropical tuna species under its management: yellowfin, skipjack and bigeye.
The IOTC adopted its first yellowfin rebuilding plan in 2016, on the back of scientific evidence that the stock was being fished at unsustainable levels. The measures mandated reductions in catches aimed at rebuilding the stocks, but didn’t impose a total catch limit or define a fixed limit for each member.
A decade later, with the scientific committee concluding that the status of T. albacares has improved, the focus of the negotiations turned toward distributing fishing opportunities.
“The adopted measure represents progress toward a more stable management framework for Indian Ocean yellowfin tuna,” Holly Koehler, vice president of policy and outreach at the nonprofit International Seafood Sustainability Foundation (ISSF), said in an email to Mongabay. “But we remain concerned that the measure does not yet fully align with the IOTC Scientific Committee’s advice, particularly because the potential catch levels under the agreement remain above the science-advised level.”
The TAC was set at 436,867 metric tons during the meeting, while the IOTC’s Scientific Committee recommended levels around 421,000 metric tons.
Several experts told Mongabay that the recommended lower catch improves the chance of a sustained recovery and reduces the likelihood that recent gains will be reversed.
“ISSF’s concern is that while the new measure includes commitments intended to reduce catches over time, the potential catch levels under the measure remain well above the level advised by scientists — possibly jeopardizing the health of the recently recovered [Indian Ocean] yellowfin tuna stock,” Koehler said.
“This is a disappointing outcome for one of the region’s most historically overfished species and is a step backwards at a time when many of the world’s other regional fisheries management organizations are moving to more sustainable, science-based policies for valuable tuna species,” Glen Holmes, senior officer for international fisheries at The Pew Charitable Trusts, said in a prepared statement.
Trade publication The Fishing Daily quoted Xavier Leduc, a representative of Europêche, which promotes European fishing interests, saying that “The EU quota was preserved while allowing substantial coastal states’ fisheries development.” Leduc also praised the EU’s efforts to bring yellowfin tuna out of the red (through implementation of measures under the rebuilding plan) as well as its work to preserve the improved status.
Environmental groups have long criticized the EU for playing an obstructionist role at the IOTC negotiations, promoting the interests of its fishing lobby over sustainability concerns. EU vessels have operated in Indian Ocean waters for more than three decades, and the bloc is a dominant player in the fisheries there. Many coastal nations in the region without a history of industrial tuna fishing are seeking to expand their domestic tuna fisheries. They blame historical overfishing by the EU fleet for severely depleting yellowfin tuna populations and threatening the livelihoods of small-scale fishers as well as the viability of industrial fishing for domestic fleets.
This has led to heated negotiations, with members often vying for larger allocations for their own fisheries sectors while overlooking ecological concerns.
Even the TAC agreement itself is considered by some scientists and advocacy groups an interim arrangement rather than a fully science-based management system. Currently, while the scientific committee provides technical recommendations, the final measures are decided through negotiation among IOTC members.
The Maldives government, which hosted the meeting, along with nonprofits like Pew and ISSF are pushing for the adoption of a management strategy evaluation (MSE), a process for establishing these harvest rules. Under an MSE, allowable catch would be decided by running simulations and modelling future scenarios. Proponents contend such a process would be more responsive to changes in stock health and less vulnerable to political wrangling.
Work on setting up an MSE for yellowfin tuna is already underway, and it could be adopted as soon as next year.
The IOTC is also concerned with the health of tuna-adjacent species like swordfish (Xiphias gladius). It is one of the target species in Indian Ocean fisheries and is also at risk of overfishing. The commission has a management measure for swordfish that limits catch to 30,527 metric tons a year for 2026-2028. However, this year, the intergovernmental body further defined this measure by determining enforceable catch limits for individual members.
At this meeting, the IOTC also made progress on reducing bycatch of sharks and rays. Manta and devil rays, collectively referred to as mobulids, are especially at risk in tuna fisheries. In the Indian Ocean, a region subject to extensive fishing pressure and where monitoring is weak, their habitats overlap with those of targeted tuna species. Fishing crews until now have had little incentive or training on how to handle these marine creatures. The rays reach sexual maturity relatively late, have long gestation periods, and give birth to only one to three pups at a time, leaving their populations extremely vulnerable.
The IOTC laid down guidelines for their handling and release to reduce bycatch mortality among mobulids.
“It was unfortunately a mixed bag however — they retained an exemption for artisanal fishers to target [mobulids], and included some voluntary language that weakened the policy,” Melissa Cronin, a marine scientist at the University of Massachusetts Dartmouth, in the U.S., told Mongabay in an email.
IOTC members also considered the RFMO’s role with respect to the High Seas Treaty, which came into force in January this year. The treaty creates potential overlap with the IOTC, because both are concerned with marine areas that lie beyond national jurisdictions. At the RFMO meeting, the parties adopted a resolution to support the work being done under the High Seas Treaty and coordinate positions on matters related to high seas governance.
“In a major milestone, IOTC became the first RFMO to adopt a binding measure that describes how it will engage on the new High Seas Treaty,” said Holmes from Pew. “This will ensure its seat at the table when treaty members begin their negotiations on marine protected areas.”
Banner image: A yellowfin tuna captured for electronic tagging off the coast of Seychelles in the Western Indian Ocean. Image by Marc Taquet via Ifremer (CC BY 4.0).
Citation:
Cronin, M. R., Murua, J., Croll, D. A., Hutchinson, M., Lezama‐Ochoa, N., Lopez, J., … Moreno, G. (2025). Evidence for a fisher‐designed solution to manta and devil ray bycatch in tuna fisheries. Conservation Biology, 40(1). doi:10.1111/cobi.70150
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