Reproduction of the Common Coral Trout Plectropomus Leopardus (Serranidae: Epinephelinae) from the Central and Northern Great Barrier Reef, Australia

The reproductive biology of the serranid fish, Plectropomus leopardus, was studied from samples collected from mid shelf reefs in the central Great Barrier Reef and mid shelf reefs and waters adjacent to Lizard Island in the northern Great Barrier Reef. For the two locations, a spawning period was observed from September through November, during which multiple spawning occurred. An inverse relationship between fat and gonad weight was observed for the coral trout, indicating that these deposits of mesenteric fat are probably being used in the processing of gonad products. The mode of sexual development, monandric protogynous hermaphroditism, was confirmed through histological analyses of gonad material. The sex structure of the sampled population was analyzed based on age and size information. The size and age of first reproduction for females was 32 to 36 cm FL and 2 to 3 years of age. Size and age distribution of females overlapped with size and age distribution of males over a wide range, indicating that sex change can occur over a broad range of sizes and ages but females were significantly smaller and younger than males. While at the present point it is not clear how sex change is determined for the coral trout, the variability observed in the size and age in which sex change occurs and in the process of transition itself suggests that behavioral processes could be involved.