Groper; Western Blue
The western blue groper is the second largest species within the wrasse family, growing to 1.6 metres. Large, fully grown males are a rich dark blue colour whereas juveniles and females vary in shades of green and grey. Juvenile western blue groper occur in estuaries and sheltered bays in seagrasses and algae, moving offshore with increasing size to coastal and offshore reefs to a depth of around 40 metres. Western blue groper feed on shellfish, small crabs and barnacles, fish, molluscs and starfish which they crush with their peg like teeth. At 25 years of age, they can reach a length of 80 centimetres, however they may be as old as 50 years by the time they reach their full size. Similarly to the Balchin groper, the western blue groper are protogynous hermaphrodites, where they changes sex from female to male at about 50 centimetres. They are a very long lived fish species. Research undertaken on the fishes ear bone (otolith), which has calcified growth layers similar to that of growth rings in a tree trunk, suggest they live up to 70 years old.
The western blue groper occurs in temperate, southern Australian waters between Port Phillip Bay, Victoria to the Houtman Abrolhos Islands, WA. Fewer groper are being sighted north of Perth due to high fishing pressure on the species population. Being an inquisitive species this makes the groper an easy target for spear fishermen.
Occurrence at the Busselton Jetty:
Immature female western blue groper are a common sight from the underwater observatory. They may be observed solitary or in a small group of up to five individuals indiscriminately biting great chunks off the invertebrate covered jetty piles in search for tasty morsels. A variety of other fish follow to clean up any discarded scraps. Many have been seen feeding on red bait crabs, indicating that these are among their preferred diet. They tend to be residential fish, as the same few are spotted on a daily basis. We are able to determine this is the case as two have had distinctive injuries that have been healing over during the last 6 months.
Image by: O.Rynvis