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Website home>Newsletters>September 2009>Diving with Bumphead Parrotfish

Diving with Humphead Parrotfish

Bumping Coral Reefs into Balance

Devouring coral reefs as they go, bumphead parrotfish travel in large schools, excreting a fine mist of sand that will end up on a romantic tropical beach nearby.

Bumphead parrotfish - photo courtesy of Klaus E. Fiedler

It is an unforgettable experience to be surrounded by them as they coolly go about the business of feeding themselves and protecting the health of the coral reefs at the same time.

You'll recognise them immediately by their distinctive, teeth that look like a parrot's beak. Despite not being beautiful in the traditional sense, divers scramble for photo opportunities of these large greenish fish with a large bump on their pink heads. Let's find out why ...

Bumphead Parrotfish Fact Sheet

Family name: Scaridae
Order name: Perciformes
Common name: Bumphead, Giant humphead, Green humphead, Double-headed parrotfish and other variations on these names
Scientific name: Bolbometopon Muricatum

Distinguishing Features

There is no difference between the markings on the male or female humphead. Growing up to 130 cm and 46 kg, they are the largest parrotfish. Looking like a parrot's beak, their teeth plates are only hidden by thick lips. Starting out as a greenish brown colour, the juveniles are distinguished by 5 lines of whitish dots spread vertically along their sides. As they grown into adults, their head grows a large bump and their colour is an array of dark grey to turquoise-green or olive, with pink or yellow faces.

Not to be confused with the juvenile Napoleon wrasse, which have 2 descending black lines behind their eyes.

Behaviour

Meet Bumphead parrotfish scuba diving the Red Sea - photo by Eric Madeja

Bumpheads are gregarious creatures, swimming in large schools from 20 up to 100 members and spending their days in close proximity to the coral reefs they feed on. You could be minding your own business exploring the reef and suddenly have a stream of humpheads racing past you, munching coral as they go, seemingly oblivious to your presence.

On a night dive, you will find them sleeping in the shallows, seeking shelter in wrecks and caverns.

Feeding Habits

Preferring to eat coral and the benthic algae that lives on it, humpheads are classified as corallivores. The juveniles keep to the safety of the seagrass beds in the shallow coral lagoons, while the adults feed on the seaward side, every so often bumping their heads into the reef to loosen bite-sized chunks of coral.

An interesting fact about white tropical beaches: the fine sand contains coral that is first ground up by the the bumphead's pharyngeal teeth and then anything not assimilated is passed out to form the necessary coral sediment. This might put a damper on your next romantic moonlit stroll, but it is all for the best in terms of coral reef resilience. The humpheads devour up to 5 tons of reef carbonates each year and are vital coral sand creators.

Reproduction

Primarily beginning life as females, even the male bumpheads possess hermaphrodite characteristics which enable them to transform into males when activated in a pre-reproductive phase that coincides with the lead male dying.

Spawning activities take place in the early morning during a lunar cycle. The humpheads assemble near gutters, promontories or in channel mouths, forming 100-strong shoals, swimming close together. The courtship seems to happen spontaneously whereby 2 fish will separate from the group and ascend to the surface with their stomachs touching. Just below the surface they release a mist of eggs and sperm, then regroup with the other bumpheads.

Life Cycle

Dive with Bumphead parrotfish in Koh Surin, Thailand - photo courtesy of ScubaZoo

Carried by the current, the hatchling larvae fend for themselves. First subsisting on algae, they move on to seaweed as their primary food source when they reach the cover of the seagrass beds in the lagoon shallows. It takes up to 3 years for them to develop sufficiently in order to forage with the adults on the outer reefs.

The bumpheads grow slowly and only begin reproduction once they reach 60 cm, which is just under half their full-grown length of 130 cm at 40 years of age. This results in a slow replacement rate.

Predation

Sharks are their natural predators, but humans pose the greatest threat to their survival. The humpheads' need for familiar sleeping grounds and the huge shoals they form while resting make them easy targets for night fishermen. Bumpheads are considered important in certain cultural events and ceremonies on the islands. These interesting fish that are best seen while taking part in a spectacular wall dive, are now sought after in aquariums across the world.

Distribution

Although they have been almost fished to extinction in certain oceans, their numbers are increasing in Marine Protected Areas and can now be found near coral reefs across the Indian and Pacific Oceans. The largest numbers of humpheads have been recorded on the Great Barrier Reef of Australia, in Malaysia and Micronesia.

Habitat

The bumphead relies on coral for food and can never be found very far from coral reefs. Resting in the shallows at night, they seek refuge in wrecks and caverns. As the new day dawns the juveniles hide amongst the seagrass on the sandy lagoon floor. The adults spend their day foraging the outer fringing and barrier reefs up to depths of 30m.

Ecological Considerations

The humphead's survival is in a delicate position due to over-fishing. Consequently they have been listed as a Management Unit Species (MUS) in the Coral Reef Ecosystems Fishery Management Plan of the Western Pacific as well as being classified as 'vulnerable' on the World Conservation Union (IUCN) 'Red List of Threatened Species'.

Thankfully the economic benefits of maintaining healthy coral reefs as diving destinations are becoming apparent to the governments of island communities. A growing trend of declaring these areas as National Parks and issuing bans on night and spear fishing is positively contributing to conservation efforts. Hopefully more countries will get on board with imposing these regulations to ensure the survival of humphead parrotfish for many dives to come.

Dive Sites

You can find the bumphead parrotfish can be found throughout the Indo-Pacific region, with the best Dive The World destinations being: the Great Barrier Reef - Australia, Sipadan - Malaysia, and Ras Mohammed - the Red Sea.


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