Dolphins are increasingly feeding near fishing boats — and that’s a bad sign
Off the coast of Italy, dolphins are increasingly following fishing boats in search of food. At first glance, this might seem like clever and even amusing behaviour: a trawler plies the seas, with dolphins swimming behind it and picking up the fish.
However, scientists believe this is a cause for concern. If dolphins are feeding so frequently near trawlers, it may mean that it has become more difficult to find their usual prey in the Adriatic Sea.
The study has been published in the journal *Frontiers in Mammal Science*.
Details
The authors observed fishing vessels off the Italian regions of Veneto and Marche. Over several years, they carried out 859 surveys of trawlers and found that dolphins regularly follow the vessels, particularly those dragging nets along the seabed or through the water column.
The researchers monitored trawlers in the Adriatic Sea between 2018 and 2025. They checked whether bottlenose dolphins — a species commonly found in coastal waters — were following the vessels.
The results were striking. In the Marche region, dolphins followed 76 per cent of the bottom trawlers surveyed. In the Veneto region, the figure was lower – around 26% – but this is still a significant proportion. On average, dolphins followed 41% of bottom trawlers and 35% of mid-water trawlers.
However, dolphins hardly ever followed beam trawlers – only in about 1.5% of cases. Scientists suggest that this may be due to the design of the nets and the type of catch: it is probably more difficult for dolphins to find suitable food near such vessels.
Why do dolphins follow vessels?
Whilst operating, a trawler brings fish and other marine animals to the surface; some of the catch is damaged, some is discarded, and some becomes easy prey. For a dolphin, this is almost a ready-made ‘cafeteria’: there is no need to expend so much energy hunting on its own.
Dolphins may scavenge discarded fish, catch weakened prey caught in the nets, or try to snatch fish right next to a moving trawl.
This behaviour is not new in itself. Dolphins have long been able to use human activity to their advantage. But the problem lies in the scale: if the majority of dolphins in the area regularly feed near fishing vessels, this no longer looks like a random trick, but rather a dependence on the fishing industry.
Why this is a bad sign
The authors of the study link this behaviour to the state of the Adriatic Sea. The seabed of the Adriatic has been subjected to intensive bottom trawling for decades. Such nets literally ‘comb’ the seabed, damaging ecosystems and affecting fish stocks.
Many large predators in this region have already disappeared or have become rare. Bottlenose dolphins remain among the last remaining large marine predators in such areas. If even they are increasingly seeking food in the wake of trawlers, this may indicate that the natural food chain has been disrupted.
Put simply: the dolphins haven’t just found a convenient way to grab a bite to eat. It may be that the sea has become so depleted that this risky method of foraging has become more advantageous for them than their usual hunting.
Why this is dangerous for the dolphins themselves
Feeding near a trawler is not safe. Dolphins can be injured by fishing gear, become entangled in nets or die. Furthermore, constantly being near vessels means noise, stress and potential hearing damage.
This is important because dolphins rely heavily on their hearing. They use sound to communicate, navigate and locate prey. If the animals are regularly near noisy vessels, this can alter their behaviour and disrupt their normal lives.
Researchers also note that feeding in the wake of trawlers may affect the dolphins’ diet, social bonds and communication.
How did the scientists realise that these were not isolated incidents?
The researchers did not simply count the dolphins near the vessels. They photographed the animals’ dorsal fins in order to identify individual specimens.
It turned out that in Veneto, around 86 per cent of the adult dolphins tagged had been photographed behind trawlers at least once, and in Marche, the figure was over 90 per cent. This suggests that the behaviour is widespread amongst the majority of the local population, rather than being limited to just a few particularly bold animals.
The authors estimate that there may be more than 1,000 bottlenose dolphins in the two regions studied combined. And, judging by the data, the majority of them regularly use fishing vessels as a source of food.
Why we cannot say that trawlers ‘help’ dolphins
At close range, trawlers do indeed provide the dolphins with an easy meal. But that does not make trawling beneficial.
The problem is that trawlers themselves are one of the causes of the destruction of the marine environment. They damage the seabed, affect fish stocks and alter the ecosystem. This creates a vicious circle: the sea is being depleted by intensive fishing, whilst dolphins are increasingly forced to feed near the very vessels that are contributing to this depletion.
The authors state explicitly that continuing trawling is undesirable not only for the protection of dolphins, but also for the conservation of marine biodiversity as a whole.
Background
The Adriatic Sea is part of the Mediterranean Sea, where fishing is carried out very intensively. Bottom trawling is considered one of the most destructive methods of fishing, as it affects not only the target species but also the seabed.
For dolphins, this creates a twofold problem. On the one hand, trawlers provide an easy source of food. On the other, they alter the environment on which dolphins depend in the long term.
Researchers believe that if destructive forms of trawling are reduced or banned, the ecosystem could gradually recover. As adaptable animals, dolphins should be able to revert to more natural behaviour.
Source
Study: Giovanni Bearzi, Silvia Bonizzoni, Nathan B. Furey, Randall R. Reeves — “Bottlenose dolphin reliance on trawlers in prey-depleted Adriatic Sea regions”, Frontiers in Mammal Science, 2026.