The Queensland grouper or giant grouper is one of the largest ray finned bony fish in the ocean and takes the crown for the largest on coral reefs. They are part of the family Serranidae which includes cod, coral trout and the much smaller anthias. In Australia the Queensland grouper is a protected species and catching and taking one can land you a pretty hefty fine and even prison time. The reason they are so heavily protected is because they are particularly vulnerable to overfishing. However in other parts of the world no such protection exists and they are targeted for their tasty flesh and also caught as juveniles for the aquarium trade. These large fish are quite curious and bold and will approach divers closely. They are not generally considered dangerous to humans however Due to their large size and appetite to match they should be treated with caution. They have been implicated in attacks, some fatal, on humans although a lot of these are unconfirmed.
They are a tropical species and can be found across the Indo-pacific region from Africa all the way east to Hawaii. In Australia part of their distribution is in temperate waters starting at Rottnest Island in the south west of Western Australia north across the top and then south down to the southern coast of New South Wales. This species is most common in shallow waters although it can be found at depths of around 100 meters. They will occupy a range of different habitats like coral and rocky reefs, caves and will even make a home under jetties, around boat ramps and in shipwrecks. Juveniles prefer to live on coral reefs and are rarely spotted.
This species is extremely large and when fully grown can reach lengths up to 3 meters and weigh in at 400 kilograms, definitely earning them the name giant grouper. Adults of the species are a grey/brown colour with a mottled patterning which helps them to camouflage in their environment. The juveniles are much more striking to look at, they are yellow with irregular dark bars and patterns. Like other species in the family serranidae these guys have extremely large mouths which allows them to swallow prey whole.
Queensland groupers have quite an appetite and are opportunistic ambush predators. This means that they are not particularly active and do not actively chase prey down but sit and wait for an unlucky animal to swim by a little too close. They will usually rest motionless on the bottom or hover in place, only moving their pectoral fins slightly to maintain their position in the water. Once a tasty animal swims close enough to eat the grouper will stick fast, they open their large mouths wide and extend their jaws which creates a type of suction and the unfortunate animal is swallowed whole. They are not fussy and will eat just about anything that swims within range including fish, sharks, rays, crabs, crayfish and even sea turtles.
Strangely enough these fish actually live their life as both a male and female. They are what is kn ion as sequential hermaphrodites, they begin life as a female and as they age will change sex and permanently become male, before they change they will go through at least one breeding event as a female. The reason for this is that the reproductive outputs for this species are higher in males and therefore it is more beneficial for the fish to be males. Once they have undergone the change to male this species commonly lives to over 30 years old however it is believed that they have the ability to live even longer, to an estimated 100 years.
Here in the Whitsundays the Queensland grouper is not a common site so spotting one of these giants is definitely a treat. The best place to spot them is around the islands on a yacht where they may turn up at the bar of your boat to make an easy dinner of the fish attracted to the lights.
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