Fish Of The Great Barrier Reef
For many of the visitors to the Great Barrier Reef it is the beautiful fishes that make the whole eco system so interesting. With an estimated 1500 and possibly as many as 2000 species of fish on the Great Barrier Reef it is easy to understand why they leave us in absolute awe. Interestingly it is possible to find at least 200 species in just one hectare, which is terribly exciting when you are planning to dive and snorkel.
Surprisingly the bulk of fishes on the Great Barrier Reef belong to just a few family groups. After diving and snorkelling on the reef it becomes quite easy to not only recognise these groups but also start to categorize them, by their shape, colour as well as behaviour.
Damselfish: Usually gather in large schools, hovering above the reef and feeding on plankton. You quite often see a school above a large head of staghorn coral and just by the snap of a finger they will all dart into the safety of its surrounds. They range in size from approx 6cm to about 14cm. Even though they are quite small they can be quite brave. The common male Farmer Damsel will dart out at a diver, taking many swoops at you as a warning to stay clear of his nest of eggs. He will bite which feels rather like being pinched.
Wrasse: These amazing fishes can change sex from female to male. They are very colourful and feed on small invertebrates. They usually live on the bottom or mid water and get around in small groups or pairs with the male dominating. They do not care for their eggs, which rise to the surface. Many a dive sight has the friendly Maori Wrasse waiting to greet you, and quite commonly he will be called Wally? The small species in the family are approx 10cm and some species can grow up to a monestrous meter in length.
Butterfly Fish: These beauties are well renowned for their gorgeous colours and patterns and their graceful beauty whilst swimming. They feed on live corals and when they find their partner it is a lifelong bond. The average butterfly fish is approx 12 -14 cm but some of the larger grow to about 25cm.
Angelfish: These fish are closely related to the butterfly fish and are in some ways just as beautiful. They feed on sponges and small invertebrates. The larger in the species will produce a large drumming sound when it is agitated. Sizes are from approx 10cm up to 35cm.
Cardinal Fish: A little like the damsel however the Cardinal is nocturnal. He hides in coral formation and caves and crevices during the day and comes out at night to feed on small shrimps and crabs. His colours are quite subdued, and his eyes are quite large. The male fertilises and cares for the eggs inside of his mouth. They are a small species with sizes from 6cm to about 12cm.
Groupers and Basslets: This group includes some of the largest of fish on the reef. These guys can also change sex when needed. The large Queensland Grouper can grow up to 270cam and weigh in at around 400 kg. The smaller Basslets are around the 10cm mark. Included in this group is the very sort after Coral Trout. He is quite commonly the blackboard special in many a seafood restaurant.
Parrotfish: These guys are closely related to the Wrasse, and are spotted and clearly heard scraping the algae from the coral. When they do this their beaklike mouth consumes quite large amounts of the coral, which is ground up and discarded with their faeces. It is quite a common sight to see powder like substance coming from them when they dart around. Young Parrotfish and females are drab next to beautifully coloured males. However they are able to change from Female to Male when needed. The parent does not care for the eggs. Their average size is 20 to 30 cm however some species can grow up to around 100cm.
Surgeonfish: When you spot these guys they will be more than likely in schools in which they will not even be all of the same species. The name surgeon comes from the scalpel like bone which projects from each side of the tail base. They feed on algae that covers the coral. They mainly resemble a plate in shape and range in size from around 20cm to 45cm.
Blennies: These little guys are territorial bottom dwellers. They are either alone or in small groups. They lay eggs in crevices as well as under rocks or even empty shells. The male then guards them until they hatch. They are very cute little fishes that on average are around 5 to 12 cm.
Gobies: Another bottom dweller, which are scattered all over the reef, they are in fact the most abundant of the fishes. So you don't miss them look closely at the surface of corals rocks and sponges as well as in the sand and rubble. Like the Blemie they also look after their eggs. They are usually only 4-5cm in length.
Triggerfish: In the summer months Triggerfish get busy building their nests in preparation for the laying of their eggs. To make their nests, the Triggerfish lay on the sandy ocean bottom and blow water out of their mouths to create a small crater. They clean the sand of any rubble by picking it up with their teeth and discarding it over the edge. The Trigger fish lay their eggs on the bottom and become fiercely protective of them. The eggs resemble a clump of small bubbles. Divers are strongly encouraged to stay away if they see a nest as the Triggerfish may become aggressive in their nature if they feel their eggs are in danger. This change in behaviour for the normally docile Triggerfish will last for about two or three months so all divers beware. Triggerfish are characterised by cone-shaped heads with eyes set far back from the mouth and well-developed dorsal and anal fins. Tritan triggerfish can grow to 50cm and are powerful. Luckily the breeding season is limited to summer.
Anemone or Clown Fish: These beautiful fish is by far the most photographed fish of the sea. Their dainty, fun and playful movements fascinate divers and snorkellers the world over. The Great Barrier Reef is no exception. When hearing a dive brief on a particular site the Dive Master will always point out where the Anemone is situated and it is here you will find them. The fish have a close association with the anemone; they nestle down into the host's soft fleshy tentacles and acquire immunity from their deadly stings by slowly covering themselves with a layer of mucus from the anemone. Initially they get stung but once they have enough mucus on them the anemone assumes it is only touching it's own tentacles. If the fish leaves it's host for a day or so it loses it's immunity and must rebuild its coating. The fish is safe from predators in its host as they will be stung if they venture too close. Anemones generally like shallower places and attach themselves to hard corals. When you come across them, stay a while - the clownfish antics will really delight you.
There is a growing concern about the effects of fish feeding on the reef. While this gives visitors an opportunity to observe fish close at hand, the types of food being offered are often inappropriate. Steak, chicken, cooked prawns; pasta and bread may seem like a good diet but not for fish. They cannot digest the saturated fats and acids in meat, cooked prawns shells contain indigestible chitin and bread and pasta can damage their livers. Fruit and vegetables are not so bad but they are not as nutritious as algae/plankton and pieces are often to large for herbivorous fish which come to be fed. Fish will often snatch at these foods when they thrown in the water but in reality they fill the fish up without providing the nourishment received from natural foods.
Apart from the nutritional aspects, fish can become dependant on a source of food, which will not always be there, and it may attract larger numbers or species of fish which do not naturally inhabit that area. In addition, artificial feeding can also change the behaviour of the fish. They can become aggressive and even dangerous to swimmers. On the other hand, fish which have become naturally tame are very vulnerable to fishing.
Feeding may also have detrimental effects on other parts of the reef when large amounts of extra nutrients are added to the water. For example, excessive growth of algae can damage the coral. Water quality may be affected, especially if fish feeding is used as an excuse for dumping of rubbish at sea.
Great Barrier Reef Marine Park Authority has developed new guidelines for fish feeding on the reef. Tour operators who wish to feed fish must have a permit endorsed and display a laminated copy of the guidelines at the site. Food must consist of fresh, raw, marine products or aquaculture fish food pellets as approved by the authority. The amount of food used is to be further restricted to 1kg per day or 2kg per day if more than one site is used.
It would be a pity if thoughtless pollution of the marine environment led to the complete banning of fish feeding. Hopefully a sensible approach will avoid adverse environmental impacts