Ecology of Botany Bay. II. Aspects of the Feeding Ecology of the Fanbellied Leatherjacket, Monacanthus chinensis (Pisces : Monacanthidae), in Pisidonia australis Seagrass Beds in Quibray Bay, Botany Bay, New South Wales

Abstract

The fanbellied leatherjacket, M. chinensis, was found to ingest fresh seagrass as a major part of its diet. Other important food items were gammarid amphipods, carid shrimps and several species of epiphytic algae. All food items were of seagrass bed origin.

Microscopic examination of gut contents suggested that seagrass and algae did not appear to be digested by the fish, but ¹⁴C-labelling of the plants showed that significant amounts of the labile carbon compounds were removed and assimilated during digestion.

The fanbellied leatherjacket was found to feed in the seagrass beds during the day, probably relying on eyesight for detecting food. Variations in tide height did not seem to affect their feeding pattern.

The amounts of seagrass, algae, amphipods and shrimps removed by M. chinensis in Quibray Bay were calculated and compared with the availability of each of these foods. Grazing by M. chinensis had little effect on seagrass and algae production rates and standing crops, but probably had a significant influence on carid shrimp and amphipod populations.