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The threats to whales and dolphins in the UK from fishing gear

Thousands of whales, dolphins and porpoises die in fishing gear in UK waters every year. It is a serious welfare issue and, for some populations, such as the common dolphins who live off the south and south west coasts of England, it is a threat to their survival.

Accidental entanglement in fishing gear is known as ‘bycatch’, and the species most affected around the UK are harbour porpoises and common dolphins. When the bodies of whales and dolphins wash up on UK beaches, post-mortems are carried out. Bycatch has been the major cause of death in harbour porpoises and common dolphins since these regular examinations were introduced in 1990.

Harbour Porpoises

Harbour porpoises are worst affected by what are known as bottom-set gillnet and tangle net fisheries. These are nets that are anchored to the seabed and hang in the water, like a wall. As harbour porpoises feed on or near the seabed, they can easily become entangled.  These high levels of bycatch may be unsustainable across the countries of the North Sea, with estimates of around 1,500 deaths each year by the UK fleet alone. These deaths represent a real threat to the conservation of porpoises around the UK, and they are a serious welfare concern.

Harbour porpoise © Charlie Phillips
Harbour porpoise © Charlie Phillips

Common Dolphins

For common dolphins, the major threat comes from pelagic trawl fisheries such as the UK sea bass pair trawl fishery and the Irish albacore pair trawl fishery. These fisheries drag a net through the water behind a boat, or pair of boats, which scoops up everything in its path. Other fisheries, including gillnet fisheries, are also taking a toll. Every winter, large numbers of bycaught dolphins wash up on French and southern English coasts, and increasingly on Irish coasts. This shows us that many common dolphins are dying out at sea in this region.

Information gathered by scientists and conservation groups about the individuals who wash up on beaches provides an essential part of the puzzle. Recent strandings analysis shows that the number of common dolphin deaths is likely to be much higher than previously thought. This is because the bycatch observations undertaken on-board fishing vessels do not provide reliable enough data, being poorly designed and limited in reach, and revealing only about 10% of the total bycatch in the area.

Humpback whales

In Scottish seas, humpback whales might not be recovering from the old whaling days, as they are in some other parts of the world, because of entanglement in static creel lines. These are the ropes that are used to secure pots to the seabed to catch shellfish such as lobster and crab. About half of the minke whales who wash up around the Scottish coastline bear signs of entanglement.

Humpback whale
Humpback whale

What is being done?

As in most of the world’s fisheries, we don’t know the true scale of the issue because the monitoring of fisheries is limited. However, the number and scale of pelagic trawl fisheries operating in waters to the west and south-west of the UK (mainly comprising large fleets from other EU countries), together with the number of bycaught dolphins washing up on surrounding beaches, suggest that thousands of dolphins, porpoises and whales - possibly many thousands are dying every year. This is likely unsustainable and it is unacceptable.


The UK Government has acknowledged the problem. In 2003 they published ‘the UK Small Cetacean Bycatch Response Strategy’ as a step towards finding a solution. Trials have been running since 1998 to investigate the effectiveness of acoustic deterrent devices (‘pingers’) on static or ‘set’ nets. Pingers are small, electronic devices attached to fishing nets that emit sounds at the frequencies to which dolphins and porpoises are most sensitive. The aim of pingers is to produce a sound that either causes them to avoid the area, or alerts them to the presence of the nets.

The UK trials revealed a dramatic reduction in harbour porpoise bycatch when pingers were used on the nets. But, the devices are costly, require maintenance and may interfere with the setting and hauling of the nets for UK fisheries. While this technology has proven to be very effective in the US, the efficiency of pingers used in the UK has been observed to decrease over time and also when used in commercial fisheries rather than controlled trials. In response to the high dolphin bycatch rate recorded in the UK sea bass pelagic pair-trawl fishery, mitigation trials using pingers began in 2001. However, pingers have not been shown to be effective for species other than harbour porpoises and may result in disturbance issues.

Dolphin escape hatches

Further trials in this fishery focused on the development of a dolphin exclusion device. This is a selection grid (typically made of steel bars) positioned within the net that allows fish to pass through and further into the net, but which deflects any dolphins upwards to one or more escape hatches in the top of the net. This exclusion device was also trialled in combination with pingers. These trials have produced mixed results and, after six seasons of monitoring and development work, the trials have yet to produce a workable and successful configuration.

What next?

It is important to make sure we don’t just move the problem somewhere else. Restrictions to reduce fishing are unpopular and difficult to impose in multi-national fisheries. In the UK, other than pingers on the nets deployed by some of the largest vessels, there are still no measures in place to reduce what is likely to remain the main conservation and welfare problem affecting whales, dolphins and porpoises around our coasts.

What can I do?

Sign our petition calling on the governments of the UK to make sure dolphins, porpoises and whales are protected from fishing gear in UK seas.

What fish should I buy?

With the exception of tuna, it’s almost impossible to know if the fish we eat comes from a fishery with a bycatch issue. This is because bycatch is not adequately considered in existing ‘ecolabels’. The best way to ensure that your canned tuna is the most dolphin friendly it can be is to buy canned tuna caught with a pole-and-line, or one-by-one fishing, where tuna are caught by fishermen one at a time, using one hook and one line. This traditional and much more selective fishing method has a significantly lower level of bycatch. Clear labelling on tuna cans is required, with labels including the tuna species in the can, where it was caught and the fishing method used. Look for labels that indicate your tuna purchase was caught one-by-one or by pole-and-line fishing; and if you are unsure ask your retailer or look online, there’s plenty of helpful information now available  It’s more tricky with other seafood but ultimately, it’s important that consumers seek out the most sustainable products available.

WDC is calling for governments, regulatory bodies and fisheries stakeholders to act urgently and decisively to end this unacceptable suffering of whales, dolphins and porpoises. This will require the collection of better data and changes to the way fish are caught including gear modifications, gear marking, and possible fishing restrictions to reduce this threat.