THE UK’s seas have seen strong numbers of humpback whales, surprising sightings of dolphins and orcas and efforts to restore oysters and seagrass in 2021.

But the Wildlife Trusts warn marine nature is being disturbed by human activities around the coasts and climate change is disrupting wildlife from fish and crabs to Wally the walrus.

The coalition of regional charities’ marine review of the year shows that by early December, Cornwall Wildlife Trust had recorded 17 sightings of humpback whales, once an extremely rare sight in UK waters.

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It brings the total to 75 sightings since 2019, with the species thought to be chasing shoals of sardines now present in the region’s waters, and shows numbers are recovering after bans on commercial whaling.

Humpbacks were also seen off the Isles of Scilly, the Firth of Forth, and off Shetland.

Two orcas from the Hebrides were spotted from the Minnack Theatre in Cornwall, in the most southerly sighting of the west coast community in more than 50 years. They also put in an appearance off the coast of Dover, in Kent.

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White-beaked dolphins were seen off Essex, far from their normal subarctic waters, while Moray Firth bottlenose dolphins were recorded on the south coast for the first time.

But more than 170 cetaceans were stranded in Cornwall alone this year – along with 247 seals, many injured by fishing activity – including a striped dolphin, a species rarely seen in the UK.

Nick the bottlenose dolphin, admired by swimmers in Cornwall, washed up in Ireland with injuries consistent with propeller damage, and a minke whale appeared in the Thames but had to be put down after its condition deteriorated.

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Daniele Clifford, marine conservation officer for The Wildlife Trusts, said: “Noise at sea caused by wind farms and other development can disorientate wildlife and cause whales and dolphins to head off course – we need to think carefully about all marine development in the future.

“Also, far too many marine creatures are unnecessarily killed due to unsustainable fishing practices, with lost and discarded fishing gear also causing havoc – especially for seals, dolphins and other marine mammals.”

The organisations also warned that people’s recreational activities are putting pressure on wildlife, with a rise in disturbance from jet-skis and motorboats causing major concern.

The National: Grey seal pup at Blakeney Point, cared for by the National Trust

The Wildlife Trust of South and West Wales witnessed a seal pup being abandoned by its mother after people were seen taking selfies with the youngster, while Dorset Wildlife Trust said large cruise ships anchored off the coast during the pandemic damaged fragile reef and seabed habitats.

Climate change is also disrupting wildlife, with marine creatures from far-flung places turning up around the British coasts.

An Arctic walrus nicknamed Wally made a splash as his progress was tracked around the UK, while a second walrus was seen off Northumberland and around Shetland.

A pufferfish, found in the open ocean and rarely seen this far north, turned up on Downderry Beach in Cornwall, possibly blown off course by summer storms.

The ringneck blenny, a small fish found in the Eastern Atlantic or Mediterranean, is now common in the Fal estuary in Cornwall.

And the furrowed crab is now abundant on all Cornish shores, outcompeting common shore crabs, and is spreading north-east to Dorset in a clear sign of climate change, conservationists said.

Extreme weather also has an impact, such as Storm Arwen which washed up hundreds of dead starfish and seal pups, as well as beaching a critically endangered Kemp’s Ridley turtle in Flintshire, North Wales.

Lissa Batey, head of marine conservation for The Wildlife Trusts, said: “It’s been a fantastic year for marine megafauna sightings, particularly in the South West, but it’s clear that our oceans are under immense pressure from fishing, development, pollution, climate change and recreation.

“All these issues are having a huge impact on life at sea.”

She said protecting the marine environment was a critical part of limiting global temperature rises to 1.5C to prevent the most dangerous climate change because healthy seabed habitats store carbon.

“We need policies that stop unsustainable fishing practices and prevent unrestricted development at sea – and we must protect at least 30% of our oceans by 2030. Future generations are counting on it.”

Projects to restore nature and tackle climate change by the coalition of wildlife organisations include restoring sea grass habitats which are home to nature including seahorses and are responsible for around 15% of carbon absorbed by the oceans.

A landmark byelaw to stop damaging fishing practices of the Sussex coast was also brought in in 2021 as part of efforts to restore nearly 80 square miles of the key habitat.

The National: Oysters

Native oysters, which have declined by 95% since the 19th century due to overfishing, pollution and disease, are being re-established in places such as Yorkshire, Essex and Belfast Lough.

In Northern Ireland, Ulster Wildlife’s “sea deep” project recorded its first juvenile skate, a critically endangered species, and if more are found it could signal that they are breeding there.

And a project to bring puffins back to the Isle of Man, including eradicating rats and using model puffins to entice birds back, reached a milestone when a pair was spotted for the first time in more than 30 years.