The first comprehensive extinction risk assessments for the 61 species of tunas, mackerels and billfishes for the IUCN Red List (Collette et al., 2011, Science, 333, 291–292) have recently been updated. The IUCN recommends re-evaluation every 10 years to determine if a species’ status has changed.
As a result of the Covid-19 pandemic we were unable to hold in-person meetings, and therefore met online with specialists to review data and population trends for species of commercial or recreational importance. Updated drafts were reviewed by participants in the 2011 assessments, many of whom are members of the IUCN Species Survival Commission Tuna and Billfish Specialist Group, and then submitted to the IUCN Red List. Assessments for seven commercial tunas (six species of Thunnus and Katsuwonus pelamis) were published in 2021, and for 10 billfishes and two small Thunnus species in 2022.
The remaining species were reassessed using information from Tunas and Billfishes of the World (Collette & Graves, 2019, Johns Hopkins University Press) and recent literature reviews. Draft species reassessments were sent to specialists for final review. As of May 2023, all 61 species assessments have now been submitted for publication on the IUCN Red List. A summary of the findings was presented at the Joint Meeting of Ichthyologists and Herpetologists in Norfolk, Virginia, in July 2023. This summary emphasized that the Red List focuses on species, not populations. One population of a species may be severely overfished while other populations of the same species may be healthy, so the species might still be assessed globally as Least Concern. For example, the Atlantic bluefin tuna Thunnus thynnus was originally categorized as Endangered in 2011 but is now Least Concern. However, the Western Atlantic population has been slower to recover and is still overfished.
Overall, 17 of the 61 species changed Red List category, 10 to a category of lesser extinction risk and seven to a category of greater extinction risk. The status of several species of commercially important tunas has improved (Juan-Jorda et al., 2022, Science, 378, 6620). This is partly a result of more sustainable fishing methods (Murua et al., 2023, Frontiers in Marine Science, 10, 1074340), better regulations, better enforcement of existing regulations by the Regional Tuna Fishery Management Agencies, and the conservation efforts of organizations such as the International Seafood Sustainable Fisheries Foundation. However, the conservation status of several smaller scombrids that are under the control of individual countries, such as the three species of Indian mackerels of the genus Rastrelliger, appears to have worsened as a result of overfishing and the use of gill nets with a mesh size so small they catch fish before they are old enough to reproduce. Seven species remain Data Deficient because of a lack of data on population trends.
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