Fishes

Firefish - one of the most distinctive reef fish

There are over 1500 species of fish living on the Great Barrier Reef.

The Coral Reef contains more species of fish than any other marine habitat. On this site, we have loosely divided them into six broad categories:

• Colourful coral associates, like clown anemone fish and butterflyfish;
• Cryptic fish like blennies, gobies and seahorses that are hard to see because of their camouflage or where they live;
• Grazing fish, like blue tangs, parrotfish and wrasse;
• Pelagic reef associates like batfish and fusiliers;
• Reef predators like snapper, emperors, cod and grouper; and
• Nocturnal & cave dwellers such as eels, scorpionfish, squirrelfish and soldierfish.

Yellow and Blueback Fusilier / Caesio teres / Family Caesionidae

Emperor Parrotfish / Scarus rubroviolaceus / Family Scaridae

Fish characteristics

The characteristics of a fish include a skeleton made of bone, one gill opening on each side of the head, a swim bladder and reproduction through external fertilisation.

The overall structure of the fish is presented as streamlined, however the head, trunk and tail are clearly identified. Fish vary widely in size, shape, colour and behaviour.

Fish skin comprises two layers: an outer skin or epidermis and an inner skin or dermis. Most fish are covered in scales. A fish's skin and scales protect it from the saline environment in which it lives, and enable it to move more efficiently through the water.

Reef fish and colour

Reef fish are able to see colour, and their bright colours are important for species recognition and protection. Colour patterns can also act as a warning to other animals that some fish are poisonous, for example, firefish. The use of colour as camouflage enables fish to ambush prey and hide from predators.

Flatfish, such as rabbitfish, are able to change their colour patterns to suit the colour of the surface they are resting on. Lizardfish are so well camouflaged that smaller fish don't see them until it's too late and they become a meal.

It is not by chance that reef fish have special colour patterns and live where they do. These adaptations help them fool their predators, defend themselves and hide from danger. The colour patterns even help them find fish of the same kind (species) among the amazing colours and teeming life of tropical reef waters.

A porcupine fish

Statistics

The smallest reef fish is a goby that is one centimetre long and weighs less than a gram. The largest bony fishes of the reef are giant cod and grouper that weigh up to 400kg.

Habitat

Fish occupy an almost endless variety of habitats. Their adaptations and responses to the environment are often difficult to study and understand. Most fish live under water, in oceans, rivers, lakes, ponds, or aquaria. Some species, such as mud skippers and lung fish, are able to survive out of water for long periods and can breathe both above and below the water.

Reproduction

Most fish are very fertile. Most species release large quantities of eggs annually. When the eggs hatch, most baby fish are on their own, and they know instinctively how to swim and find food.

Surgeon fish have protective spines at the base of their tail

The majority of fish species on the Great Barrier Reef produce a mass of tiny eggs which float away, and never have any further contact with their parents.

A number of small fish like gobies and damselfish attach their eggs to shells or bits of coral and guard them until they hatch. The tiny larvae (young fish) are then left in the open water to fend for themselves.

Feeding

Fish feed on almost all available food on the reef ranging from algae to other fish.

Protection

Reef animals use their shapes, body parts and behaviour in many different ways to help them survive.

Many fish have protective spines. The aptly named surgeon fish (Acanthurus) have very sharp 'blades' at the base of their tails, members of the scorpionfish family have poisonous spines on their dorsal fins that give powerful stings. The well-camouflaged stonefish have strong dorsal spines and a potent venom.