10 species you might not know live around our UK seas 

Seahorse

There are two species of seahorse found in UK waters: the Short Snouted and the Long Snouted (also known as the Spiny) seahorse. Unsurprisingly, the main difference between them is the length of their snout. At around 15cm they’re half the size of a typical ruler.  

Both species can change colour to act as camouflage – seahorses aren’t the fastest of swimmers so they rely on concealment tactics to avoid being eaten by predatory fish.  

These seahorses are found all around the UK - populations have even been found in the Thames! They tend to stick to shallow, sheltered waters where they can hide and use their tail to cling onto seagrass and seaweed.  

Most fascinating is the way that males give birth to young (known as ‘fry’). The female passes eggs to the male, who looks after them until they hatch.

Photo credit: Long Snouted seahorse female sheltering in common Eelgrass, Studland Bay, Dorset © Alex Mustard / naturepl.com 

Harbour porpoise

The harbour porpoise is the smallest cetacean (the group that includes whales, dolphins and porpoises) we have in the UK, and at around 1.5m long it’s the second smallest porpoise in the world.  

It takes a newborn harbour porpoise less than 30 hours to develop full hearing – this is the fastest of any mammal, on land or sea.  

The UK is home to around 170,000 of these shy and elusive creatures, which need to feed almost around the clock to survive. Their nickname is the “puffing pig” after the sound they make when coming up to breathe. 

Find out more about the threats to this porpoise and our work to protect them. 

Photo credit: Harbour porpoise off the Isle of Man © naturepl.com / Florian Graner / WWF 

Leatherback turtle

When you think of leatherback turtles, images of exotic beaches might come to mind, but the abundance of jellyfish around the UK’s coast from time to time provides a great source of food for these giants. They make the marathon journey across the Atlantic Ocean, following the warmer Gulf Stream, which brings them all the way to our shores. In fact, Wales holds the world record for the largest marine turtle ever discovered: in 1988, a leatherback was found measuring 2.5 m long, 2.5 m from flipper to flipper and weighing over 900 kg (that’s about the same as a small car)! 

Photo credit: Leatherback turtle © Jürgen Freund / WWF

Nudibranch

Nudibranchs (pronounced nudi-branks) are colourful sea slugs with amazing abilities. They get their colouring from their food and some even use the poisons of the prey they eat to defend against predators. 

Their name means ‘naked gills’ and relates to the frilly gills found on their backs - they basically have their lungs on the outside of their body  

Some species of nudibranch are able to photosynthesise like coral and others even have detachable organs – they’re not your standard slug! 

Photo credit: Nudibranch on a kelp leaf, Norway © Wild Wonders of Europe / Magnus Lundgren / WWF 

Orca

Despite being known as 'killer whales', orcas are actually the largest species of dolphin.  

Orcas are intelligent animals with varying hunting techniques (including herding and slapping prey with their tails), which they use to eat most marine mammals, seabirds, fish, sharks and octopus, amongst other things. 

There’s a resident pod of eight orcas who live off the west coast of Scotland. They’re an isolated, older group, and it’s feared that they may have high levels of pollutants in their bodies, so sadly no calves have been born for many years.  

Photo credit: An orca near the Shetland Isles, Scotland © naturepl.com / Chris Gomersall / WWF 

Sunfish

The sunfish is the heaviest bony fish in the world and produces the most eggs of any vertebrate. They are summer visitors to our waters, attracted by the jellyfish which are their main source of food. Marine litter is a big threat, as they can mistake plastic bags for food. 

They get their name because they like to bask in the sun, on their sides, at the surface, perhaps to warm up after being in colder waters. 

Photo credit: Sunfish © naturepl.com / Alex Mustard / WWF 

Basking sharks

Basking sharks are the second largest fish in the world. They are gentle giants and can be spotted around the coast of Britain, swimming slowly, basking in the sun. They swim near the surface with their huge mouths wide open, filtering plankton from the water to eat. 

They can measure up to 11m long and weigh up to 7 tonnes, making them the largest fish in British waters and almost the same weight as a London bus! 

Photo credit: Basking shark feeding on plankton around Cornwall © naturepl.com / Alex Mustard / WWF 

Bottlenose dolphin

Bottlenose dolphins are beautiful, sociable animals. They’re one of the few species, along with apes and humans, that have the ability to recognise themselves in a mirror.  

Bottlenose dolphins sleep with one half of their brain at a time, and keep one eye open. It's believed they do this to keep an eye out for their group - to make sure they stick together - and to look out for predators like sharks.  

There are thought to be three resident pods of bottlenose dolphin around the UK - one in Cardigan Bay, Wales; one in the Moray Firth, Scotland; and the final one in Cornwall. 

Photo credit: Bottlenose dolphin © Andrey Nekrasov / WWF 

Angel Shark

The Angel Shark is one of the rarest sharks in the world and is critically endangered. Thought to be clinging on around the warmer waters of the Canary Islands, their rediscovery in our waters is very new and offers a glimmer of hope for their survival.  

These “flat sharks” are well camouflaged and are likely to be found on the sea floor, where they lie in wait to feed on small fish and molluscs. 

Photo credit: Angel Shark © Philippe Guillaume

Pink Sea-Fan

The Pink Sea-Fan is a soft coral and grows at an extremely slow pace – it can, however, live up to 50 years. They use their stinging tentacles to catch tiny, microscopic animals. This coral, like many others, is sensitive to climate change causing changes in water temperature.

Not many people know we have such a range of coldwater corals in the UK – and they’re just as important as in the tropics for the species that depend on them. 

Photo credit: Pink sea fan, Devon © naturepl.com / Linda Pitkin / WWF