Guide to Irish Marine Life

Information courtesy of "Great British Marine Animals, 2nd Edition" by Paul Naylor

  Corkwing Wrasse

Crenilabrus Melops

The overall colour is variable with females, generally a pale brown, and males a darker more greenish brown, with hints of blue or dark red. Breeding males have superb colouration with brilliant blue or mixed green with claret.

 Plaice

Pleuronectes Platessa

A common flatfish frequently found on sandy and muddy seabeds, or on sand patches in rocky areas. The background colour is usually grey-brown but this can change to blend in with the seabed; the underside is usually a pearly white.  Plaice are actually lying on their sides. Newly hatched from the floating egg, tiny flatfish look like conventional fish with the body positioned vertically in the water and an eye on either side. By the time the young fish have settled on the seabed, one eye has moved over to join the other eye on the same side of the body, thus producing their typically twisted expression.

Pollack

Pollachius Pollachius

Seen both singly and in shoals, the pollack is a very common fish in Irish waters. The pollack is a member of the cod fish and conforms to their typical pattern of three dorsal and two anal fins, though there is no chin barbel.

Black Goby

Gobius Niger

Gobies are very abundant small fish, occassionally confused with blennies. Gobies have a swim bladder and move with a graceful, darting movement. 

Butterfish (or gunnel)

Pholis Gunnellus

This eel-shaped fish is named after its slippery skin, and is distinguished by the row of white-edged black spots along the base of its dorsal fin. They are often found in crevices or creeping around the base of kelp plants. Their eggs are laid between December and March.

Compass Jellyfish

Chrysaora Hysoscella

Easily identified by the attractive radial pattern of brown V-shaped markings on its "umbrella" or "bell". An additional dark circle in the centre of the pattern completes the appearance of an old-fahioned compass rose. Twenty-four slender tentacles hang down from the edge of the umbrella while there are four more noticeable arms in the centre.

Little Cuttle

Sepiola Atlantica

The little cuttle's buoyancy is less sophisticated than that of the common cuttlefish but it can hover effectively or jet away quickly.  The tiny clouds of ink released when disturbed are used effectively in combination with colour control. A predator's attention can be distracted to follow the ink cloud and the cuttle escapes unnoticed. Little cuttle live on sandy bottoms.

Tompot Blenny

Parablennius Gattorugine

Though usually small, tompot blenny are among the most charismatic and inquisitive fish in Irish waters. Their distinctive, clown like faces can be seen peering out from crevices in reefs or rocks.  Like all blennies, tompots lack the buoyancy of a swim bladder and swim with a clumsy though surprisingly rapid, wriggling motion.

Common Prawn

Palaemon Serratus

A common sighting in the nooks and crannies of wrecks and rocky reefs, and frequently found in groups. The front two pairs of legs bear nippers, which are used to pick up small pieces of food as the prawn walks across the seabed. Prawns can also swim, either backwards in rapid bursts using the fan tail or forwards using the small flaps beneath the abdomen for propulsion. 

Sea Hare

Aplysia Punctata

The sea hare gets its name from the broad upper pair of head tentacles that look like hare's ears. It has large flap-like lobes on its back and there is a much reduced shell hidden by the soft tissues. The sea hare is a hermaphrodite like all sea slugs and any individual can act as either a male or female to another.

John Dory

Zeus Faber

The John Dory has a body shaped like a flat oval plate on edge. Other notable features are the large head with its mournful expression, the very long dorsal fin rays and a single dark spot in the centre of each flank. While not a rapid mover, the John Dory shows great manoeuvrability when stalking its prey and swims tilted at all sorts of angles, even upside down! Encounters with divers tend to happen in shallow waters as it hunts the two-spot gobies.

Velvet Swimming Crab

Necora Puber

The most notable features are the bright red eyes and the blue lines on its legs and claws. Like all swimming crabs, the final section of the rear-most pair of legs is flattened to form a swimming paddle.  When encountered these crabs may rear up and spread their claws in defiance rather than shrinking away into a crevice. They hunt fis, prawns and bottom dwellers such as worms and molluscs.

Common Hermit Crab

Pagurus Bernhardus

Very abundant on both rocky and sandy seabeds, and small individuals are often found in pools on the shore. Adult hermit crabs actually occupy the larger shells of a whelk (type of underwater snail), as their own shell is shed at a young age to allow for growth. Hermit crabs are versatile feeders and can prey on other animals, scavenge on bottom deposits or filter food from the surrounding water.

Spiny Spider Crab

Maja Squindo

Spiny spider crabs cn often be found on most seabed types, often resting in the open or wandering free rather than hiding in crevices.  Spiny spider crabs have a varied diet, eating seaweed and encrusting animals.