|Western Blue Groper
Scientific Name: Achoerodus gouldii
The Western Blue Groper is found from the Abrolhos Islands off Geraldton in Western Australia to west of Melbourne. It lives in waters from five to 65m deep.
The western blue groper is actually a member of the wrasse family. In southern Australia, the western blue groper is the largest carnivorous bony fish species living on reefs, reaching a length of up to 1.7 metres once they are fully grown, at about 30 years.
Like the eastern blue groper, the western blue groper can change sex over their lifetime. All western blue groper begin life as females, and some, but not all change to males later in life.
The western blue groper uses it’s strong peg-like teeth to prise off reef animals such as sea urchins, molluscs and crustaceans. Adults have an unusual ‘bite and suck’ feeding behaviour, where they dislocate their jaw so as to bite off a large piece of reef algal mat – and then filter-out and eat the tiny crustaceans that live in it.
The western blue groper has few natural predators once fully grown.
Western Blue Groper can live up to 70 years. They reach maturity at around 15 – 20 years.
They prefer to live in small groups, consisting of one male, one or two females and several juveniles. The male fish is always the largest one in the group.
If the male is removed from the group (e.g. by fishing, predation or old age), then the group’s dominant female takes the male’s place – by changing sex and colour.
Western blue groper are very closely related to the eastern blue groper (Achoerodus viridis). The separation of the two species can be traced back to the last Ice Age.
IUCN Red List – Lower Risk (conservation dependent)
This species is very vulnerable to heavy fishing, as it is extremely long lived, taking many years to reach sexual maturity and even longer to be able to change sex from female to male.
Probably due to its long life span and size, large specimens are very inquisitive when they encounter divers. This behaviour makes them vulnerable to spearfishing, which can lead to localised stock depletion.
Fortunately, in recent years, many dive clubs and individual divers have become aware of the pressure on blue groper populations and have changed their behaviour from spearfishing for the gropers to simply enjoying a friendly underwater interaction with them.
To download the complete Fact Sheet from the Department of Fisheries WA website click here: