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The impressive and friendly Wrasse frequently provides close-up encounter on The Great Barrier Reef

Chances are you will see at least one species from the colourful wrasse family on your dive or snorkel adventure with ABC Scuba Diving Port Douglas, as they are the second largest family of fishes in Australia. The word “wrasse” comes from the Cornish word wrath, meaning an old woman or hag, yet these fish do not look as you may imagine a hag to appear. Lined, checkered or leopard-spotted, with reindeer-antlers or Pinocchio-like noses, wrasse come in a variety of colours and shapes. You may think you have seen two different species, but as they age and reach sexual maturity, wrasse can change colour and sex!

Wrasse are meat-eaters, feeding upon small invertebrates and fish, and follow larger predatory fish to eat the trail of left-overs that they leave behind. They have thick lips with a row of teeth that usually face outwards. Their mouth is protractile, meaning it is capable of extending forwards.

Generally, wrasse are a small fish, with most species measuring less than 20 centimetres, however the largest in the family, and a regular sighting on our dive adventures, is the humphead wrasse.

Humphead Wrasse

This colourful, friendly fish has many names; Humphead wrasse, Napoleon wrasse, and Maori wrasse (Cheilinus undulatus). It is easily identifiable by its size (it is the largest fish in the Labridae family reaching up to 2 metres in length and weighing 190 kilograms), its thick lips, the intricate pattern of lines behind its eyes, the hump on the forehead and its personable nature. Due to a noticeable decline in populations, this iconic fish is now protected within the Great Barrier Reef Marine Park and numbers are increasing again.

They have a very important role to play within the ecology of the reef as it is one of the few fish to eat sea hares, boxfish or the toxic crown of thorns sea star, which has devastated the Reef with regular plague-like outbreaks over the last 50 years.

Humphead wrasse begin life as female, appearing more grey and pastel in colour. Some members of the population will change gender and become male at about 9 years of age, turning vivid greens and blues. They are long-lived with females living up to 50 years of age. They have slow breeding rates, reaching sexual maturity between 4 to 6 years. When ready to spawn, the adults move to the down-current end of the reef and form a spawning aggregation with sexually mature adults from adjacent reefs.

This spectacular fish is a frequent visitor at one of ABC Scuba Diving Port Douglas’s regular dive sites and loves interacting with snorkelers and divers alike. An incredible fish and experience to share.

Cleaner Wrasse

One of the most common and easily identifiable wrasse is the bluestreak cleaner wrasse, Labroides dimidiatus. These wrasse set up an underwater “car-wash” or beauty salon for other fish to visit. You will spot them darting around gills or in and out of fishes mouths, but they aren’t risking their lives each time they do this. Instead, they are removing unwanted parasites or dead tissue from these fish. This relationship provides food and protection for the wrasse, while providing its’ clients with health benefits.

When a potential client first nears the cleaning station where these wrasse are based, the cleaner wrasse will perform a dance by moving their rear up and down. The potential client will recognise them as a cleaner fish due to the lateral stripe running the length of its body and this dance-like pattern. To accept their cleaning service, the client fish will allow the cleaner wrasse access to its body surface, gills and mouth by adopting a species-specific pose.

These potential clients need to be careful though, as some fish will mimic the cleaner wrasse. The sabre-tooth blenny is one such fish. When the client fish accepts the service of this mimic fish, instead of consuming the parasites, they lunge in and tear off a small piece of flesh! This is bad news for actual cleaner wrasse, who may lose a client as they seek a safer cleaning station away from the imposter.

Rockmover Wrasse

The rockmover wrasse, Novaculichthys taeniourus, got named for their behaviour while searching for prey. They will work in pairs. One will grab, pull or push small stones or reef fragments, while the other waits until the prey has been uncovered,  and then will quickly grab the uncovered prey and eat it.

As a juvenile this wrasse resembles a reindeer, with the first two dorsal fin spines forming “antlers” over the fish’s forehead. As they mature the “antlers” are lost. If you are lucky to spot this juvenile you are in for a beautiful sight as they sway back and forth in the current to mimic a piece of drifting seaweed.

 

Humphead Wrasse+Humphead Wrasse


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