Dietary characteristics of the ecologically-important fish species Centroberyx gerrardi, including discussion of resource partitioning among species of Berycidae in Australia

Data for the Berycidae, collected during extensive past scientific surveys, were used to quantify the depth distributions of the four species of Centroberyx and two of Beryx found in Australian coastal waters and thus elucidate the extent to which these species are partitioned by region and depth. The dietary, jaw and dentitional characteristics of the ecologically and fishery-important Centroberyx gerrardi were then determined, providing the first such account for any Centroberyx species. While Centroberyx gerrardi, Centroberyx lineatus, Beryx splendens and Beryx decadactylus are found throughout southern Australia, the last two species extend further up the west and east coasts. Centroberyx australis occurs on the lower half of the west coast eastwards to the central south coast and Centroberyx affinis on the lower half of the east coast. The four Centroberyx species typically occur at depths <350 m and the two Beryx species at >350 m. On the south coast of Western Australia, depth distributions undergo an overlapping progressive gradation, from C. lineatus in inshore and nearshore shallow waters, to C. gerrardi and C. australis in nearshore deep waters, and then B. splendens and B. decadactylus in offshore deep waters. The main dietary categories of C. gerrardi change with increasing body size from crabs and isopods in small fish to teleosts in the largest fish, in which volumetrically they constituted >60% of the stomach contents. The wide range of teleost prey (at least 39 species from 33 families) ingested by C. gerrardi would be valuable to this species if continuing climate change or other anthropogenic effects lead to alterations in the composition of potential prey. Differences between depth distributions account for the fish prey of C. gerrardi comprising nearshore species, such as those of clupeids, congrids, pomacentrids and platycephalids, whereas those of B. splendens (from studies elsewhere) are dominated by myctophids, which are abundant in deeper waters. The combination of a large mouth and numerous, exclusively small teeth (edentulate morphotype) strongly suggest that C. gerrardi is a suction feeder adapted to engulfing larger prey. While the co-occurring and likewise commercially-fished Oplegnathus woodwardi also ingests substantial volumes of crabs and teleosts, its diet is distinguished from C. gerrardi by large volumes of poriferans and appreciable volumes of echinoderms, likewise reflecting feeding specialisations. Although differing in depth distributions and dietary compositions, berycid species in general are close to the apex of the food web.