Large lutjanid and serranid fishes in tropical estuaries: Are they adults or juveniles?

Two serranid fishes, Epinephelus coioides and E. malabaricus, and 2 lutjanid fishes, Lutjanns argentimaculatus and L. russelli, are common in estuaries of northeastern tropical Australia. Reviews of the literature suggest that, at least for E. coioides, E. malabaricus and L. argentimaculatus, both juveniles and adults occur in estuaries. I conducted the present study to determine if estuarine populations of these 4 species did in fact contain adults, or if they were comprised entirely of juveniles. I collected E, coioides, E. malabaricus, L. russelli and L, argentimaculatus from estuaries in northeastern Australia. I compared the size, age and reproductive maturity of fishes from estuaries to fishes of the same species from offshore areas. The estuarine populations of all 4 species seemed to consist entirely of reproductively immature fish. All fish from the estuaries possessed immature gonads, and for both serranids (protogynous hermaphrodites) all were females. Furthermore, all fish from the estuaries were much smaller and younger than the largest fish of the same species from offshore. This implies that estuaries are important juvenile development grounds for these lutjanids and serranids.