Divergence of the growth characteristics and longevity of coexisting Platycephalidae (Pisces)

Divergent age and growth characteristics can reduce deleterious competitive interactions between taxonomically related species facilitating coexistence. Five platycephalid fish species, Platycephalus caeruleopunctatus, Platycephalus longispinis, Platycephalus richardsoni, Ambiserrula jugosa and Ratabulus diversidens, inhabit inner continental shelf habitats along the east coast of Australia. We tested the hypothesis that the age and growth characteristics of these five species are unique. The age of each species was estimated by counting the number of opaque zones in sectioned otoliths. The maximum observed age ranged from 4 years for A. jugosa to 16 years for P. longispinis. von Bertalanffy growth functions were fitted to length-at-age data for each combination of species, sex and location and compared using likelihood ratio tests. The age and growth characteristics of each species were unique and each species displayed sexually dimorphic growth, with females growing larger than males. The unique species-specific growth characteristics may assist length-based partitioning of resources, reducing competitive interactions and facilitate coexistence between these platycephalid species.