Why dolphin deaths are on the rise in Britain

The number washed up on UK shores has doubled in 12 years

The plight of the dolphin first came to public attention in the early 1990s, when substantial numbers of dolphin carcasses were washed up on the shores of South West England.

The dolphins were the victims of "by-catch" – caught up in the nets of large fishing boats trawling the English Channel and Atlantic approaches.

Since then, the annual number of dolphins washed up or stranded on UK shores has doubled, from 360 in 1994 to 719 in 2006. Experts believe that the real death toll is much higher, however, due to the large number of deaths which occur out at sea and leave no coastal evidence.

Large-scale commercial fishing is a high-growth industry, and the range and intensity of methods is increasing. The intensive methods used in some fisheries, however, are disastrous for dolphins and other cetaceans.

The increase in beached dolphins throughout the past 13 years, for example, is largely attributed to the growth of pair-trawling for sea bass, whereby vast nets are dragged at relatively high speeds between two vessels.

As air-breathing mammals, dolphins, porpoises and other cetaceans become asphyxiated when trapped in fishing nets, unable to reach the water's surface to breathe. Post-mortems on suspected by-catch dolphins reveal many signs of struggle and distress including broken teeth, skin lacerations and bloody fluid in the lungs.

Work in the UK and Europe aims to address the problem. Research projects to design escape hatches from trawl nets and develop other methods of deterring dolphins from approaching fishing nets are underway.

Regulations which require fisheries to implement dolphin-friendly precautions have also been introduced in the UK. However, large numbers of smaller fishing boats use bottom-set gill nets, a method which is known to cause many porpoise deaths, but these areexempt from the regulations. Additionally, although the regulations are in place, they tend to be poorly enforced.

Becoming entangled in fishing nets is not the only man-made danger facing the already-endangered cetaceans. The destruction of their natural food sources through over-intensive fishing, damage to their habitat, chemical pollution and distress caused by noise disturbance also heavily impact dolphin populations.

In 2007, declared Year of the Dolphin by the UN as part of its decade of education for sustainable development, organisations such as the RSPCA are calling for stricter enforcement of by-catch legislation and more research into alternative fishing technologies in a bid to reduce cetacean mortality.