Zooarchaeology and Genomics Reveal Human Overexploitation of Atlantic Bluefin Tuna

By analysing both ancient and modern DNA samples, researchers from the University of Bologna have offered a new perspective on how human activity has shaped the fate of bluefin tuna and marine ecosystems over thousands of years.

The study examined 49 modern specimens (collected between 2013 and 2020) and 41 ancient ones (some dating back 5,000 years), taken from different areas of the Mediterranean and Atlantic. The results show that genetic erosion and population decline in Mediterranean bluefin tuna began nearly a century before the industrial-scale overfishing that took off in the second half of the 20th century—marking a clear break from the preceding millennia of genetic stability.

“Our research shows that historical overexploitation of bluefin tuna had a profound impact not only on the species’ abundance, but also on its genetic makeup, which had remained surprisingly stable until the 19th century,” said Adam Andrews, lead author of the study.

Among the most surprising findings was evidence of shared genetic material between tuna caught in Norway and the eastern Mediterranean and those from the Gulf of Mexico—suggesting that these Atlantic spawning grounds play a crucial role in maintaining the genetic diversity of Mediterranean populations. Despite these links, DNA-based demographic models show that the Mediterranean population began declining as early as the 19th century.

"This international and multidisciplinary research, led by the University of Bologna, has produced one of the most remarkable genomic datasets ever created for a marine species—combining, for the first time, complete genomes from both ancient archaeological and modern samples. This unique resource for evolutionary and applied research is now available to the scientific community. These findings provide a powerful tool to rethink management and conservation goals for this resource,” emphasized Fausto Tinti, professor of Zoology and principal investigator of the study.

“In this study, we applied the most advanced methodologies currently available for ancient DNA analysis. Reconstructing ancient and historical genetic dynamics allows us to quantify human impact and establish more precise recovery margins. “Ancient DNA is a window to the past that helps us look to the future with greater awareness,” commented Elisabetta Cilli, paleogenomics expert and senior author of the article.

The study, resulting from an international collaboration between marine biologists, geneticists, and zooarchaeologists, is a concrete example of how integrating the sciences of the past with present-day challenges can guide more effective strategies for the conservation of marine resources. The analyses were conducted at the Laboratory of ancient DNA (aDNA Lab) of the Alma Mater Studiorum – University of Bologna, one of the few laboratories in Italy meeting international standards for handling highly degraded DNA, such as that extracted from ancient and historical specimens.

“The millennia-long evolutionary and demographic history of Mediterranean bluefin tuna is written in its DNA.

 This study shows us how urgent it is to protect not only the populations but also their genetic diversity, which is key to future resilience,” concluded Alessia Cariani, professor of Zoology and senior author of the study.