Reef predators include some of the largest fish on the reef, such as groupers and many medium-sized fish such as rock cod, snapper and emperors. Please note that those other well-known reef predators - sharks and rays - have their own section.
Rock cods and Groupers
This is a large group of fish ranging from the small, colourful basslets to the large Queensland grouper. The majority of species have three spines on the gill cover (operculum) and a large mouth with more than one row of teeth. Generally these fish ambush prey using their colouration patterns for camouflage. The fairy basslets form large aggregations on the reef fronts where they feed on zooplankton. When approached they quickly seek shelter amongst the coral.Most species are hermaphroditic, with adult females capable of changing sex to become male. Male fairy basslets are easily differentiated as they have a different colour patters to the numerous females in a colony. In a large school there may be a number of males with separate territories within the school. During the summer months, coral trout migrate to form spawning aggregations where, like most other members of the family, they spawn at dusk. After a courtship period the male and female rush towards the surface to release eggs and sperm.
Many species of this group are of commercial value. However, fish among this group are among the worst offenders for causing ciguatera poisoning. There are size and bag restrictions for these fish within the Marine Park. The Queensland grouper, potato cod and barramundi cod are Protected Species in the Great Barrier Reef Marine Park, and all individual cods and groupers over 100 cm are also protected. Another giant fish, the Humphead Maori wrasse from the wrasse or Labridae family, is a protected species too.
Snapper are small to medium sized reef fish. Most are nocturnally active predators feeding mainly on fish, crabs, shrimps, gastropods, cephalopods and planktonic organisms. Snappers, and in particular the red emperor (Lutjanus sebae) which is the snapper family, not the emperor family, are a favourite angling species. Chinaman fish (Symphorus nematophorus) are frequently implicated in ciguatera poisoning.
Emperors are a keenly sought group by both recreational and commercial fisheries. They are normally found over sandy areas adjacent to reefs where they forage for crabs, sand dollars, fish and other bottom-dwelling organisms.
Spawning amongst the sweetlip emperor (Lethrinus miniatus) occurs nearly year round off Cairns, from June-August off Townsville and from October-November in southern waters due to variations of water temperature. Juveniles live in shallow water seagrass beds and mangroves, moving offshore as they grow. Sex changes from female to male occur as the emperor grows. Unlike the sweetlip emperor, the spangled emperor (Lethrinus nebulosus) has molar teeth which enable it to crush shellfish.
Coral trout - a colourful reef predator