Many people were not aware of the laws against disturbing dolphins, whales and porpoises – or that they risked fines for breaking them, said Whale and Dolphin Conservation (WDC) and the National Wildlife Crime Unit (NWCU).

Wildlife charities are calling for people spending time at the sea this spring and summer to give space to dolphins and other marine mammals they see, watching from a distance and not crowding them.

Marine animals have been enjoying quieter waters around the UK since the pandemic started, with bottlenose dolphins regularly spotted along the Blackpool coastline in the first lockdown, and orcas and dolphins seen off the coast of Northumberland.

But as the latest lockdown eases and visitors flock to the coast, the marine charity WDC fears a rise in incidents of people disturbing animals with leisure craft or other recreational activities, or attempting to jump in and swim with dolphins.

Marine mammals are affected by disturbance from human activity, especially when they have youngsters, are resting, feeding or socialising, and can be scared off from important habitats or even injured or killed.

Most disturbance is accidental, because many boat users and holidaymakers do not know how to behave around dolphins and other wildlife, and are not aware of the rules protecting them or how to report incidents.

Cetaceans such as whales, dolphins and porpoises are protected under UK law against reckless or deliberate disturbance, harassment, killing and injury, with fines of up to £5,000.

Though prosecutions were rare, WDC said staff and volunteers regularly saw incidents where dolphins and other animals were disturbed by people, and received reports from concerned members of the public.

The wildlife charity is raising awareness of the issue and encouraging people to reduce their impact on whales and dolphins. Tips include watching from the shore, keeping a safe distance in boats, being calm and quiet, checking if boat tour operators are accredited with the Wildlife Safe (WiSe) scheme for minimising disturbance to marine wildlife, and reporting any incidents.

People are warned not to chase or repeatedly approach animals, try to scatter groups, make sudden changes to speed or direction, or swim with them or try to feed or touch them.

The awareness drive has been backed by the NWCU and environment minister, Rebecca Pow, who said: “Disturbance can have devastating impacts on marine mammals up and down our coastline, including dolphins. I urge all of those visiting the coast to familiarise themselves with the guidance, and help protect them.”

Katie Dyke, from WDC, said: “UK seas are a special place for dolphins and whales, being home to 21 species – more than anywhere else in northern Europe. They are also a rapidly growing destination for marine recreation and tourism, which is increasing levels of disturbance.

“Many species are seen close to shore and disturbance happens when people get too near to marine wildlife, disrupt their natural behaviours and cause them stress.”

Ch Insp Kevin Kelly, head of the national wildlife crime unit, said: “If your behaviour has a detrimental effect on a dolphin you could be committing an offence.