The last dolphins forced to follow fishing boats to survive: new study reveals scale of crisis in the Adriatic Sea
- Bottlenose dolphins in the Adriatic Sea increasingly dependent on trawlers for food: dolphins in the region Veneto were observed following nearly one in four bottom otter trawlers – and even three out of four in the region of Marche
- A symptom of ecological collapse: the Adriatic is one of the world’s most overfished seas.
- Natural prey has been so severely depleted that dolphins have been forced to adapt their behaviour to survive
- OceanCare calls for an accelerated phase-out of bottom trawling in the Adriatic and sensitive Mediterranean marine areas, in line with EU law
A new scientific study by Dolphin Biology and Conservation, a partner of OceanCare, reveals that the large majority of bottlenose dolphins in the Adriatic Sea have become strikingly reliant on fishing trawlers for their food – a behavioural shift that scientists say reflects the severe depletion of natural prey in one of the world’s most overfished seas.
The study, published in the journal Frontiers, analysed eight years of survey data (2018–2025) covering 17,755 kilometres of navigation effort off the Italian regions of Veneto and Marche. Researchers observed 859 trawlers across 148 days of trawling to document whether dolphins were present in their wake.
The findings: dolphins follow trawlers to survive
The results are striking. On average, dolphins were observed following nearly one in four trawlers (24.7%). For bottom otter trawlers – one of the most destructive fishing methods – the figure rises to over 40%. In the region of Marche, three out of four (75.9%) bottom otter trawlers had dolphins following them.
The dolphins are not simply curious, they are foraging: feeding on fish trapped in the nets, extracting organisms from the outer mesh, scavenging on organisms stirred up by the gear, and consuming discarded bycatch thrown overboard. In other words, they have adapted their behaviour to survive in a sea that can no longer feed them naturally.
Photo-identification data reinforces this picture: 86% of marked adult dolphins in Veneto and 90% in Marche were photographed at least once foraging behind trawlers.
“These dolphins are not following trawlers by choice. They are doing so because the Adriatic has been so severely depleted by decades of overfishing that natural prey is no longer reliably available,” said Giovanni Bearzi (Dolphin Biology and Conservation), Co-Author of the study. “This is a stark indicator of ecological collapse, not an example of dolphins adapting successfully.”
The Adriatic: one of the world's most overfished seas
According to the UN Food and Agriculture Organisation, 63% of Mediterranean fish populations are fished unsustainably, and fishing pressure in the region is twice the level considered sustainable. The Adriatic is the most severely affected area within the Mediterranean.
Bottom trawling – dragging heavy nets across the seabed – has fundamentally transformed the Adriatic ecosystem. Rich, three-dimensional marine habitats have been reduced to flattened plains. Elasmobranchs – sharks and rays – have declined by more than 94% between 1948 and 2005. Common dolphins, once abundant throughout the Adriatic, have virtually disappeared.
The bottlenose dolphin is now the only cetacean species regularly present in the northern and central Adriatic. The fact that even this highly adaptable species has been forced to depend on trawlers for food illustrates the scale of the ecological damage.
A vicious cycle
The relationship between dolphins and trawlers is not without risk for the dolphins themselves. Following trawlers exposes them to entanglement, vessel strikes and the consumption of low-quality discarded catch. The long-term effects on dolphin health, reproduction and population dynamics remain unknown – and are the subject of ongoing research.
More broadly, the study warns that promoting the continued use of trawlers in the Adriatic is inadvisable – not only for the dolphins, but for marine biodiversity as a whole. The nets that feed the dolphins today are the same nets that have destroyed the ecosystem those dolphins depend on.
Randall R. Reeves, senior author of the study and chair of the U.S. Marine Mammal Commission’s Committee of Scientific Advisors, says:
“When a large share of marine predators shift to feeding opportunistically around fishing gear, it’s a fairly safe bet that human influence has reached a tipping point. Trailing trawlers may boost an individual dolphin’s food intake in the short term, but any benefit of this opportunistic feeding is at least partly offset by the ecosystem devastation and depletion of prey stocks that trawl gear causes.”
OceanCare calls for action
OceanCare calls on the European Union and its Member States to accelerate the phase-out of bottom trawling in the Adriatic and other sensitive Mediterranean marine areas, in line with the EU Habitats Directive and Marine Strategy Framework Directive. The findings of this study make clear that voluntary measures and gradual timelines are insufficient – the Adriatic ecosystem cannot wait.
“The EU has committed to protecting marine biodiversity. These dolphins are telling us, in the clearest possible way, that those commitments are not being met,” said Nicolas Entrup, Director of International Relations. “The answer is clear: bottom trawling in the Adriatic must be phased out – and it must happen now.“
Further information about the article published in Frontiers:
The study was conducted by Giovanni Bearzi, Silvia Bonizzoni (Dolphin Biology and Conservation; DBC is a scientific partner of OceanCare), Nathan B. Furey (University of New Hampshire) and Randall R. Reeves (Okapi Wildlife Associates). Survey data was collected between 2018 and 2025 in the Italian regions of Veneto and Marche, covering a combined area of 5,000 km².
Further Information
OceanCare’s “The Trawl Supremacy”-Report 2024
Available for interview
Giovianni Bearzi (Dolphin Biology and Conservation), giovanni.bearzi@gmail.com
Nicolas Entrup (Director of International Relations OceanCare), nentrup@oceancare.org
Images
High-resolution images are available free of charge for editorial use, provided the copyright is credited (Dolphin Biology and Conversation)
