The weird and wonderful creatures of the Irish Sea

Basking shark. Picture by Andrew Pearson

Basking shark. Picture by Andrew Pearson - Credit: Andrew Pearson

Join Cheshire Wildlife Trust’s Living Seas Officer Emily Cunningham for a virtual tour of our local seas – snorkel not required

Male cuckoo wrasse. Picture by Paul Naylor

Male cuckoo wrasse. Picture by Paul Naylor - Credit: Paul Naylor

Stand on an English beach, looking out across the blue-grey waves towards the horizon, and what do you see? A vast expanse of cold, dark, empty water? If the answer is yes then you’re not alone. Many of us believe we have to travel to foreign climes to find colourful fish, dolphins and turtles; but dip beneath the surface and you’ll find UK seas are home to a mind-boggling variety of weird and wonderful creatures.

Like the land, the seabed is a patchwork of different habitat types including sand, mud, gravel, rocky reefs and huge canyons. From the rocky reefs of Anglesey to the depths of the Lune Deep, the Irish Sea features all of these and more, each supporting their own community of species. The sea is a 3D environment, with creatures living in, on and swimming above the seabed.

We begin our journey on the shore, surrounded by habitats familiar to us from days at the seaside. Rock pools are often our first glimpse into the underwater world, where limpets graze films of algae like armoured lawnmowers among dark red Beadlet anemones, their tentacles retracted as they await the next tide.

At the foot of the rocks, you might spot what looks like muddy honeycomb – but which is in fact a living reef. Built by honeycomb worms from sand and shell, the reef structures provide shelter for other species like snails, crabs and anemones. Subtidal rocky reefs are home to many fish species, including the rainbow coloured male cuckoo wrasse, which wouldn’t look out of place on a tropical reef.

Sea pen. Picture by Paul Naylor

Sea pen. Picture by Paul Naylor - Credit: Paul Naylor

The sand beneath your chair on the beach is full of life too – although it might not appear so at first glance. Many types of worm, bivalve (shells) and crustacean live among the sand grains; but obvious evidence of their secretive lives is limited to the shells of dead organisms or, in the case of lugworms, from their sandy casts.

The wealth of invertebrates found in our estuaries and mudflats is clear from the hundreds of thousands of wading birds, like knot, dunlin and redshank that overwinter on our shores – did you know that one cubic metre of estuarine mud has the same calorific content as 16 Mars bars?

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Moving offshore, vast plains of mud support delicate sea pens – a type of soft coral that resembles an antique quill – alongside prickly sea urchins, spiny spider crabs and the delicious Dublin Bay Prawn (aka scampi). The submarine patchwork also features sand and gravel habitats, which are important spawning and nursery grounds for fish, including: flatfish, the (not so) common skate and sea bass. Sand and gravel is also home to sand eels, an important prey species for many commercially important fish, such as cod and haddock, and for seabirds, like puffins. This resource also attracts larger predators, including harbour porpoise and some of the 30 species of shark found in the Irish Sea.

Moving upwards in the water column lies the foundations of this rich marine foodweb – plankton. This saltwater cocktail is made up of microscopic, photosynthetic algae (phytoplankton), tiny creatures such as copepods (which form the greatest animal biomass on earth) and the eggs and larvae of most marine species. Excitingly, it is this smallest of life that attracts one of the biggest visitors to the Irish Sea – the world’s second largest fish, the basking shark. This filter feeder arrives to feast on plankton blooms and the Isle of Man is thought to be an important breeding habitat for the species, with courtship rituals visible from shore during the summer months. The summer swarm of jellyfish also brings large, exotic visitors to our seas, namely the leatherback turtle and the ocean sunfish – the world’s largest turtle and bony fish respectively.

Reef seascape. Picture by Paul Naylor

Reef seascape. Picture by Paul Naylor - Credit: Paul Naylor

These are not the only ocean giants to visit the Irish Sea. Twelve species of cetacean have been recorded in our local waters including the harbour porpoise, bottlenose dolphin and even the killer whale. Grey and common seals are also found locally and are often spotted basking on rocks or sandbanks.

To learn more about our incredible Living Seas or to find out about events happening in the North West this summer, visit

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