‘Scavenger’ dolphins increasingly rely on trawlers for food in overfished Adriatic, say scientists

In the Adriatic Sea, where overfishing has drastically reduced natural prey populations, bottlenose dolphins are increasingly relying on trawlers for sustenance. Scientists have observed that these intelligent marine mammals are now following fishing vessels to scavenge for food, a behavior that has become more pronounced over time. This trend highlights a growing ecological imbalance due to unsustainable fishing practices and the depletion of marine life. According to a study led by Giovanni Bearzi, president of Dolphin Biology and Conservation in Italy, the situation has reached a critical point, with dolphins learning to associate with trawlers to ensure survival.

The research team conducted extensive monitoring of trawlers in the Adriatic, inspecting 859 vessels over 148 days across two regions in Italy—Veneto and Marche. Their findings revealed a stark contrast between the two areas. In Marche, up to 76% of trawlers were accompanied by dolphins, compared to just 26% in Veneto. This discrepancy suggests varying levels of dependence on trawlers among dolphin populations. The study noted that dolphins often follow trawlers to scavenge for discarded fish and other marine organisms, a practice that has become essential in an environment where natural prey is scarce.

Giovanni Bearzi emphasized that this behavior is not merely opportunistic but has developed into a cultural transmission within dolphin communities. Young dolphins observe their mothers and elders foraging near trawlers, learning to exploit this resource. This adaptation, however, comes with significant risks. Trawl gear can injure or kill dolphins, and prolonged exposure to the noise generated by trawlers may cause hearing damage. Additionally, foraging near trawlers can disrupt their social structures and communication patterns, potentially affecting their long-term survival.

The decline of common dolphins in the Adriatic further underscores the severity of the issue. Once abundant, these dolphins have nearly disappeared except in specific hotspots, indicating a broader collapse of marine ecosystems. Bearzi pointed out that the loss of apex predators signals an alarming shift in the region’s biodiversity. He stressed that the current state of the Adriatic reflects the consequences of excessive and destructive fishing practices, which have pushed marine life to the brink.

Dr. Randall Reeves, another researcher involved in the study, highlighted the potential long-term impacts of this reliance on trawlers. While dolphins may temporarily benefit from accessing food, the associated dangers—including injury, hearing impairment, and behavioral changes—pose serious threats to their well-being. The study also notes that the availability of alternative food sources remains limited, forcing dolphins to take greater risks to avoid starvation.

The researchers advocate for immediate action to address the root causes of this crisis. They recommend reducing fishing pressure and adopting more sustainable methods to restore marine biodiversity. Bearzi expressed hope that reducing destructive fishing practices could allow marine resources to recover, enabling dolphins to return to their traditional hunting behaviors. He recalled his early career, when he focused solely on studying dolphin behavior without considering the impact of human activity. Now, he sees the urgent need to balance conservation efforts with responsible fisheries management.

This study, published in *Frontiers in Mammal Science*, underscores the complex interplay between human activities and marine ecosystems. As the Adriatic continues to face unprecedented challenges, the plight of bottlenose dolphins serves as both a warning and a call to action. The future of these remarkable creatures—and the broader marine environment—depends on addressing the unsustainable practices that have driven them to seek refuge in the wake of trawlers.