The threat of ‘supertrawlers’ to cetaceans

Environment | Oceans

By Bethan Henderson, Freelance Writer

Published December 30th, 2021

‘Supertrawlers’ are large-scale commercial fishing boats that trail nets the size of 450 tennis courts. The gaping maw of a supertrawler net is the length of seven blue whales, and when it sweeps the ocean depths, it captures large quantities of marine wildlife—not just its intended fish species.

The Sussex Dolphin Project (a part of the World Cetacean Alliance (WCA)) is fighting this issue in the UK. Their project lead, Thea Taylor, describes the situation by stating, ‘These supertrawlers have not only caught masses of their target fish species, but tonnes of fish and marine life that they do not want, including marine mammals.’

Beached dolphin in Eskmeals, England. | Kevin Cooper / Wikimedia Commons

These are usually ground down for animal feed or thrown back dead as bycatch. Bycatch is the unintentional capture of nontarget marine species during fishing expeditions, and often includes vulnerable cetaceans such as dolphins, porpoises, and whales.

In 2020, 17 dead cetaceans washed up on Sussex shores during the time supertrawlers were fishing off the Sussex coast. In the months without supertrawler fishing, only two cetaceans were found on the local beaches. 17 may not sound like many, but this number is estimated to be closer to 170 cetacean bycatch deaths in Sussex alone, since 90% of bodies do not tend to reach the shore. As a result, the Sussex Dolphin Project has called this threat one of the largest dangers to cetaceans, and one that is avoidable but increasing.

Supertrawler fishing is not just an issue in the UK. The Pelagic Freezer-trawler Association (PFA) represents nine companies and owns 23 supertrawlers that tread European waters. The PFA claims to have sustainable methods with a ‘low impact on the marine ecosystem and based on effective science-based fisheries management.’

For example, in the year 2020, the organisation introduced pingers to their fishing gear—devices that supposedly prevent dolphin bycatch, by emitting noises that scare them away. However, pingers have not yet been proven to prevent dolphin capture in any existing research.

‘Supertrawlers… make up a huge economic contribution to governments, making it easier to justify or turn a blind eye to any environmental costs.’

This points to the lack of accountability at the heart of the matter. Governments sell the rights to fish in their waters to fishing organisations, and the larger the organisation, the larger the revenue they will generate. Supertrawlers and other large-scale commercial fishing ships, therefore, make up a huge economic contribution to governments, making it easier to justify or turn a blind eye to any environmental costs.

Furthermore, because supertrawlers have the fishing rights for the Exclusive Economic Zones (EEZ), located around 200 nautical miles offshore, they are technically in international waters. This means the countries have some say, but ultimately the supertrawlers do not have to uphold territorial sea legislation. In the UK, for example, these ships are not actually bound to any of the UK’s sustainable fishing legislations.

Discarded fish in Chandipur, India. | Riddhiman Bhowmik / Unsplash

Not only does this impact marine wildlife and lead to bycatch, but this also creates socioeconomic disparity. Andrew Gillman, a Sussex fisherman for over 50 years claims, ‘Local fishermen have seen significant changes in pelagic catches…I was fined and sent to court for catching, as bycatch, a dead sea trout, many years ago. Yet the bycatch of a supertrawler must be horrific. There is no visibility as to their bycatch and a lack of understanding of the level of damage that this scale of fishing is doing to the ocean as a whole.’

This is a sentiment echoed by fellow local fisherman, Graham Doswell, ‘I don’t understand why these industrial ships have such free reign, with little in the way of checks and monitoring, while the fishing community inshore are held to such high account on each fish. Supertrawlers must have a huge impact on marine life by decimating fish species that form a vital part of a balanced ecosystem.’

Not only do these practises lack accountability, but they directly oppose the UK’s Fisheries Act 2020. Following Brexit, the UK government established new ecological objectives, including maintaining ‘environmentally sustainable’ fisheries, minimising and reversing ‘their negative impacts on marine ecosystems’ and 'incidental catches of sensitive species.’

This is not only a threat to cetaceans in the UK, but across the world, with hundreds of thousands of bycaught cetaceans dying across the globe. Not only does commercial fishing cause widespread cetacean deaths, but it has sublethal effects that are often overlooked. In fact, in 2016, the International Whaling Commission stated that fishing gear entanglement is the most significant threat there is to cetacean health.

‘In fact, in 2016, the International Whaling Commission stated that fishing gear entanglement is the most significant threat there is to cetacean health.’

Cetaceans are often injured if they escape nets, suffering from abrasions, broken bones, or significant panic and distress. There are also impacts on cetacean social groups as a result of this disruption. All of these factors are underestimated and not considered in impact assessments used to inform marine policy. Impact assessments focus on a population level, overlooking and failing to monitor damage to individuals and their social groups. Based on evidence of these consequences, studies in this area argue for a zero tolerance of cetacean bycatch.

Moreover, there are effects on an ecosystem level. Cetaceans play a role in maintaining a healthy marine ecosystem and disrupting their population could cause an ecological cascade (i.e. a knock-on effect where changes in a species’ population influences the populations of species on other trophic levels).

Cetaceans also tend to migrate long distances, increasing the primary productivity of oceans by fertilising the water with iron-rich waste, and circulating micronutrients that inform the oceans biogeochemistry. They not only provide these environmental services but are economically important. For example, whale watching is an industry that produces over two billion US dollars every year.

A bycaught vaquita porpoise entangled in fishing netting. | Christian Faesi / Flickr

Undoubtedly, other fishing methods are damaging to marine wildlife. For example, fly-shooting, where weighted nets drag along the seabed. Fly-shooters have four to eleven times as much killing power than inshore fishing boats. Despite this, Victoria Prentis, the Minister of State at the Department for Environment, Food and Rural Affairs (DEFRA), claims that they are more sustainable than other methods because the vessels require less fuel.

In countries like the Philippines, dynamite fishing (using explosives to stun or kill fish for easy collection) is illegal due to the extreme damage to coral reefs, yet it continues to be used. Therefore, not only do unsustainable fishing methods across the board need to be monitored more closely, but legislation needs to be transparent and enforced.

This is exactly what is being demanded by the WCA, which wants transparency from the PFA and stronger legislation and accountability from the UK government. Their goal is to eventually eliminate cetacean bycatch, not just reduce it.

‘The government has committed to protecting 20% of land and sea for nature by 2030 and it needs to take urgent action on this, or there will be no sea life left to protect.’—Caroline Lucas

It is important to consider that this goal applies to a specific form of fishing in a specific country, and that sustainability varies with fishing method and location. For example, most of Asia relies on fish as their primary source of dietary protein. Fishing can be carried out sustainably and is important in many places for nutrition and in culturally significant dishes.

On the contrary, the UK is not reliant on these supertrawlers to feed the country, and there are massive environmental implications that need to be taken seriously. As Caroline Lucas, the Green Party MP claims, ‘The government has committed to protecting 20% of land and sea for nature by 2030 and it needs to take urgent action on this, or there will be no sea life left to protect’.

Featured Image: Flavio Gasperini | Unsplash () ‘Role of Cetaceans in Ecosystem Functioning: Defining Marine Conservation Policies in the 21st Century.’ International Congress for Conservation Biology. . Available at: [Accessed December 22nd, 2021]

Dolman S. and Brakes P. (2018) Sustainable Fisheries Management and the Welfare of Bycaught and Entangled Cetaceans. Frontiers in Veterinary Science. Available at: [Accessed December 22nd, 2021]

World Cetacean Alliance. 'Dolphins aren't discard.' Available at: [Accessed December 22nd, 2021]

McVeigh K. (2021) ‘Damaging ‘fly-shooting’ fishing in Channel sparks concerns.’ The Guardian. Available at: [Accessed December 22nd, 2021]

Van Balsfoort G. (2020) 'Pelagic Freezer-trawler Association introduces pingers as precautionary measure to avoid bycatch of dolphins.' Pelagic Freezer-trawler Association. Available at: [Accessed December 22nd, 2021]

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