Dive Pembrokeshire UK
Marine Life Around West Wales.

Interesting links.

Pembrokeshire Islands. Learn more about the underwatre life of Pembrokeshire


Dolphin and Whale watch. http://www.ceinewydd.co.uk

Fish Data base

Great Scallop   Pecten maximus 

Stocks have been declining due to over fishing.  Large areas have been dredged. The scallop embeds itself into the sand, drawing water through the gills to strain out edible particles.  When danger approaches its shell snaps shut, it can also use this to propel itself through the water.  The Great Scallop has both male and female sexual organs and spawns in summer.  The eggs hatch into free swimming planktonic larvae, which hatch after about three weeks, and attach themselves to seaweed and sea firs.

[Image]Grey seal   Halichoerus grypus

Around 100,000 live around the coast of Britain.  It is one of the world's rare seals and may grow up to seven feet in length.  The seals are found around the Islands of Skomer, Skokholm, Ramsey and out at The Smalls.  There are areas where you can actually dive with them.  Breeding takes place in the autumn, when the males come ashore to establish territories.  A female may mate with more than one male to produce a pup of around 14kg which she suckles for three weeks, gaining 2kg per day due to the 60% fat content of the milk.  Sand eels and cod comprise the seal's main food but they will take whatever fish are in abundance. On average, a female may live until 35, ten years longer than male grey seals. 

Conger eel Conger conger

Eating anything that moves, including squid, octopus, fish and crustaceans, Conger can grow up to 143lb in deeper waters away from the coast.  As maturity approaches they cease to feed resulting in regression of all but their sexual organs. After migrating thousands of miles to depths reaching 4,000 metres to lay their eggs (up to 8 million) they then die having lived, on average, 15 years. The Moray eel is rarely seen in British waters, its bite which contains a toxin, causes blood poisoning.

Greater pipefish Syngnathus acus

The pipefish is closely related to the Seahorse, and swims in a semi vertical position. The colouring affords ideal camouflage in seaweed and eel grass,  its favoured haunts. They are rarely found in waters deeper than 18 metres. In spring and summer spawning takes place and the male accepts the eggs into its pouch. They remain there until they hatch.

Butterfish Pholis gunnellus

Slippery in nature,  with a long dorsal fin running down its back, the butterfish feed on worms and small crustaceans. Spawning takes place over January and February, and several hundred eggs are laid between rocks. The female stands guard over her eggs which hatch in about one month. Growth of the fry is slow, less than half an inch a year and the fish may live for up to ten years. They have no commercial value but make good bait for the fishermen.

Ballan wrasse Labrus bergylta

One of the most frequently seen fish when diving. There are over 300 species of wrasse, the most colourful being the Cuckoo wrasse. Young wrasse grow very slowly, but live up to 30 years old. The female spawns in June and she makes a nest out of seaweed.

Pollack Pollachius pollachius

A good sporting fish which can weigh up to 20lb. Preferring rocky waters, reefs and wrecks, pollack feed on small members of the cod and herring families, small crustaceans and sand eels.

Spawning takes place between January and April, in depths down to 100 metres. The eggs float freely, slowly drifting inshore. They are important commercially, where 250,000 tons are landed annually in European waters.

Mackerel Scomber scombrus

In 1698, the mackerel acted as catalyst for the changae in Sunday trading.  By law, the sale of this fish was allowed due to the rapid deterioration of its flesh following death.  The body of the Mackerel is designed for speed, allowing it to chase and catch schools of smaller fish. Spawning peaks around May when large shoals are seen, especially around the west coasts of Britain. During winter the fish head for deeper waters when feeding stops.

Lesser spotted dogfish Scyliorhinus canicula

This harmless species is the most commonest European shark, found mainly in the southern waters around Britain. Dogfish can be found in depths between 2 metres and 210 metres. They are bottom dwelling fish, and feed by scent rather than sight. Mating takes place in autumn, as fertilisation is internal, there is a delay of several weeks before egg laying. Egg capsules called mermaids purses, and are often washed ashore. They have a commercial value and end up in the fish-and -chip shops. It is otherwise known as rock salmon.

Edible crab Cancer pagurus

Is the largest of the crab species in Britain, and they live up to eight years old. The female mates when they are about five years old, and occurs just after moulting when she is soft. Over 3 million eggs may be laid, but few survive. Those that do, float in the plankton and grow into tiny crabs through a series of moults. Moulting takes place several times a year, but is less frequent as the crab grows. Edible crabs feed on other shellfish but are also great scavengers. Only specimens of 4 1/2 in. broad are allowed to be taken, and it is also illegal to land  these crabs with a soft shell or females with eggs.

Common Hermit crab Eupagarus bernhardus

They live in discarded shells, often of the welk. In search of food it walks on its two front legs, dragging its shell behind. It will also share a shell with other animals. After pairing with a male they will carry the eggs on her abdomen until they hatch into larvae.

Velvet Swimming crab Macropipus puber

This aggressive creature has blue-black and red markings on its legs, and dense velvety covering of fine hairs on its shell. It will eat almost anything they can find. Its main predator is the cuttlefish. As with most crustaceans if it looses a leg or a claw it will grow back again, often larger than the original. The male will carry their female partners around for weeks before mating and egg laying. The females carry the eggs around for several weeks before they hatch into larvae.

Spiny spider crab Maia squinado

Their long spindly hairy legs and squat appearance give them their name. In summer they migrate from the deeper waters to the shallow in order to mate. They congregate sometimes in their hundreds with the females, which have recently moulted, in the centre. The mating season ends in the autumn when they move back into deeper waters. The female carries up to 150,000 eggs for nine months. The plankton larvae float before settlingo on the seabed as tiny crabs. Spider crabs feed on small animals and on seaweed, and use their tiny pincers to extract food from small crevices.

Common lobster Homarus gammarus

Like the crab, the lobster periodically sheds its shell by pulling its body out through a split across the back of the shell. The new shell hardens in a few days. It sometimes eats the old shell to maintain body calcium levels. Fending off such predators as seals with its powerful claws, the lobster walks over the seabed in search for food eg. shellfish.  Females mate at seven years old when they are 10 ins long. An orange mass of 150,000 eggs are laid in late summer. For nine to ten months they are carried under the abdomen of the female. Eventually the eggs will hatch into shrimp like larvae. Lobsters will live for up to 30 years, but its the diet that determines their size and not their age.

Crawfish Palinurus elephas

Unlike the lobster it does not have large claws, but can protect itself by its spiny shell which can inflict a nasty wound. It can swim backwards, like the lobster flapping its abdomen and tail. Without front claws it feed on soft bodied animals such as worms and on dead fish. During winter the adults migrate to deeper waters to mate. Like the lobster the female carriers her eggs for several months till they hatch. They are then carried with the currents, sometimes for miles until then end up on the sea bottom. this can be miles from shore, and may not come into contact with shallow waters until they are mature. They are not eaten much in Britain, but in France they are a delicacy and are called langouste.

Spiny squat lobster Galathea strigosa

This colourful creature can be quite difficuilt to find because its flattened body enables it to hide between rocks.  However, by torchlight, its bright turquoise and orange colours are easily seen The squat lobster curls its tail and abdomen under its thorax and by straightening it out can swim in short bursts. It defends itself vigorously and can give a painful nip. Following mating, which takes place in pairs, the eggs hatch into larvae in spring and summer, floating as plankton. Squat lobster may grow up to 120mm long and are sometimes found at depths of up to 35m

Common prawn Palaemon serratus

Like a chamaelion, the common prawn can cange its body colour to match its background.  Whilst feeding, it walks on the back three pairs of legs, leaving the front pair for picking up food including small worms and bits of seaweed. The prawn is the favourite food of the fish, sea anemones and cuttlefish. In summer the male mates with a soft recently moulted female who may then produce up to 2,500 eggs which after hatching float among the plankton. Young prawns grow rapidly with each moulting taking only 20 seconds.

Sea hare Aplysia punctata

The slow moving sea hare is a link between shelled snails (eg whelk) and the true sea slugs. It is often dull brown or green with a delicate shell on its back which is hidden under the flaps.  Hermaphrodite by nature (that is displaying male and female characteristics), it is fertilised by the animal behind it. The eggs are laid out in strings, some 26 million of them stretching 20 metres in length. The sea hare was thought to have magical properties, and in Roman history its touch was said to cause vomiting and death.

Common sea cucumbers

Sea cucumbers, species of which are numerous, possess neither spines nor armour.  They rely on a unique escape mechanism to avoid danger.  When danger threatens, they eject a portion of their gut to satisfy their predator's appetite (bit of a drastic way to get rid of a stomach ulcer!).  The sea cucumber then sits tight whilst regeneration of a new stomach takes place.  Some species hide in the rocks and sand with only their tentacles visible whilst other species can only be identified with the aid of a microscope.. 

Common cuttlefish Sepia officinalis

The cuttlefish is a highly developed mollusc, with excellent eyesight, has full control over its colour and buoyancy. Like the octopus can produce a cloud of ink. The internal shell is composed of small chambers which act as buoyancy tanks. During the day they are filled with water and the animal sinks to the bottom and hides in the sand. At night the water is pumped out and it emerges to hunt. It hovers away from its prey, and when within range shoots out its hunting arms pulling the prey into its jaws. The cuttlefish can change colour by way of its coloured cells controlled by the nerves, and it is used as a camouflage. Its favourite habitat is the eel grass beds.

Common Octopus Octopus vulgaris

During the day the Octopus hides in a rocky lair on the seabed, emerging at night to hunt. Crabs are its favourite food, which are pounced on and enveloped by the web of skin between the arms. The lobster bits their prey and injects a poisonous saliva, quickly paralyses them to be eaten at their leisure. Since one Octopus will not tolerate the presence of another, the male placates the female before mating with a display of his arm suckers. They mate at arms length. the male transferring packets of sperm to the female by means of a specially adapted tentacle with a groove in it. The female lays up to 200,000 eggs which she guards for four to six weeks. She goes without food and dies shortly after the eggs have hatched. Only 200 survive.

The Octopus can grow up to 15 feet and weigh over 100lbs. They have the most complex brainof the invertebrates, and learn to solve problems by trial and error, and once learnt will always be remembered. They have an acute sence of touch and can differentiate between objects blind folded. When threatened they release a cloud of ink to confuse the enemy. The ink is toxic to the octopusand if it does not escape the ink, it wil die. Crabs and Lobsters are also killed.

Colour changes is indicated by the eyes, the cells in the skin become active to blend in with the surroundings. The chromatoplones consist of 3 bags, each with a different colour. Colouration reflects mood, white for fear, red fpr anger, and brown its usuall colour.

Common starfish Asterias rubens

All starfish belong to the echinoderms. The spines arise from a skeleton just beneath the skin, and is formed of separate bony plates. The starfish has no head but a five rayed symmetry like the petals on a flower. The feet are filled with a fluid and work by hydraulic pressure. They can pull apart shells of mussels and other bivalves which starfish eat. A single arm with the central disc attached will re grow the other four arms. Males and females shed sperm and eggs into the water at the same time during the spring and summer. Up to 2 million eggs can be released in two hours. They float in the plankton for about two weeks before settling on the bottom to develope.

There are many other starfish found along the Pembrokeshire coastline. The purple sunstar and the common sunstar are the most colourful.

Edible sea urchin Echinus esculentus

The scientific name Echinus means hedgehog. The strong suction of the tube feet allow it to cling to rocks and kelp stems. With its powerful teeth it can peel off tiny animals such as sea mats and sea firs. Predators include fish, seals and sea otters. Spawning takes place in spring and both eggs and sperm are released into the water. Larvae is developed and floats with the plankton. The urchins can travel several miles, and live for about ten years.

Peacock worm Sabella pavonina

Looks like a tube but each can extend a multi coloured feathery fan, which is retracted when threatened. These are in fact modified gills which absorb oxygen and act as a filter to trap waterborne particles. They breed by shedding both sperm and eggs into the water.

Common jellyfish Aurelia aurita

The bell expels water to propel it along. It consists of mostly jelly which acts as a primited skeleton. Its tentacles are rarely powerful enough to be painful to a human. The adult releases sperm into the water to drawn into the female. The egg develops into a small hairy swimming larva. This fixes itself to a rock, where it changes into an anemone like form called a scyphistoma. Immature jellyfish bud off from this and grow into adults.

Common anemones

Are like blobs of jelly that extend their tentacles to sting prey. Each sting is coiled in its cell until a hair like trigger is touched, then it shoots out to its victims, a shrimp or a small fish. Sea anemones will attack each other, often the larger wins, and the red and browns defeat the greens.

Dead mans fingers Alcyonium digitatum

These are soft corals and do not have skeletons but instead have limpy splinters scattered through the body to strengthen it. Small colonies are attached to rocks in shallow waters down to 20 metres. They are white or orange in colour. Food is brought to the colonies by the currents and caught in the tentacles of each polyp. Eggs are fertilised inside each polyp by sperm drawn from the water through the mouth. The eggs develop into small hairy larvae that swim out of the parent mouth to find a new surface on which to settle.

Common sea squirt Ciona intestinalis

The adult is little more than a bag with a stout outer covering, with two openings. When pocked it squirts a jet of water through its openings or siphons. The sea squirt is attached to the sea bed, filter feeding through its siphons. Large sea squirts can filter 200 litres an hour. They are both male and female and release both eggs and sperm, but at different times. The water carries the sperm and eggs on currents and there the eggs are fertilised.

Marine Eelgrass. Patamogetonacead

Found in North haven on Skomer Island. Several species of eelgrass grow in muddy, shallow bays along the coastline of cold, temperate regions of the world. It roots itself onto the bottom and bears slender, floating stems. Its tapelike leaves may be 1.8 m long. Marine Eelgrass belongs to the pondweed family.

Common Sun Star.

This animal is a member of the asteroidea class found at depths between 10-50m, often preying on other echinoderns.

Lightbulb Sea Squirt. Clavelina lepadiformis

Very comon in UK waters, this animal is a member of a group called Tunicates, this is actually a colony of separate individuals connected at their base. Found at depths down to 50m

Bristle Stars.

Found along the sand bottoms of Stack Rocks and Hen & Chicks out of Little Haven. Live among other filter feeders on gravel or clean sand. They are easily damaged, even when handled gently. Any regeneration of arms are rapid and takes place readily. They feed by raising one or more of its arms into the air and catched floating particles of planktonic organisms. This is then moved by its tubed feet and passed into the mouth.

Sea Fans.

Found around the Island of Skomer and High Point. They are beautiful in colour and row on walls and found at depths of 10 metres or more.


Marine Biology Links

Marine Conservation Society

The Marine Conservation Society (MCS) was founded in 1977. It is now the leading environmental charity in the UK dedicated solely to protecting the marine environment. It has worked successfully for twenty years to highlight issues of concern and threats to both marine wildlife and to the wider marine and coastal environment.

Its web site includes information about the work of the Society, some special projects it co-ordinates, and the wide range of books and merchandise it sells. Its book list is particularly impressive.

MCS Jersey Local Group

The Jersey Local Group of the MCS was established in October 1996 by a small group of local marine conservation enthusiasts. Its aim is:

To heighten awareness of the islandís wonderful marine life through educational, research and conservation projects.

Its web site contains details and pictures of the group's activities, along with back issues of their regular newsletter, Sea Views.

Carl Meyer's Home Page

Carl is a marine biologist from Jersey who now does research work in Hawaii. His site includes information about his projects on tiger sharks, giant groupers and reef fishes. He also has the results of his research into the Jersey spider crab which he did whilst based in Jersey before moving out to Hawaii. The spider crab research was sponsored by the Jersey Department of Agriculture and Fisheries.

Bernard Picton's Home Page

The well-known nudibranch expert, co-author of "A Field Guide to the Nudibranchs of the British Isles" (Immel Publishing Ltd. ISBN 1-898162-05-0), has a superb site with information about the nudibranchs of British waters. Lots of good images!

The site also has some useful links to other marine biology resources.

British Marine Life Study Society

BMLSS England

BMLSS Scotland

The British Marine Life Study Society is a voluntary non-profit making organisation. It publishes information and does not engage in campaigns.

Purpose and Aims

to stimulate interest in the undersea world and natural history of the seas, and related subjects.

to bridge the gap between the popular books and scientific literature by publishing readable and informative articles on marine life and the ocean environment.

to liaise and co-operate with conservation and fishery organisations and other wildlife groups.

The BMLSS site has interesting articles and some useful links.

The Marine Biological Association

Based in Plymouth, Devon, the Marine Biological Association of the United Kingdom (MBA) is the largest learned society representing the marine sciences in the UK, with an international membership of about 1500. Its site has information about its research and education programmes.

The Great British Seahorse Survey

This page on the Marine Biological Association site has information about the survey started in 1996 by Neil Garrick-Maidment and Sue Daly. Any seahorse sightings in British waters should be reported to Neil c/o nma@plymouth.swis.net or by mail to National Marine Aquarium, The Fish Key, Plymouth, PL4 0LH.

Jersey Tourism

Guernsey Tourism

Not really marine sites at all, but if you like the look of the marine life of the Channel Islands and you'd like to visit and see it all for yourself, these are the best places on the Web to start.




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