Seasonal feeding on Zostera capricorni seeds by Juvenile Penaeus esculentus (Crustacea: Decapoda) in Moreton Bay, Queensland

Abstract

The natural diet of juveniles of Penaeus esculentus Haswell (mean size 13.0 � 3.3 mm CL) collected from a seagrass (Zostera capricorni Aschers.) bed in Moreton Bay over 18 months was studied. There was a marked seasonal change in the occurrence of Z. capricorni seeds in their diet. These seeds made up to 1370 of the ash-free dry weight of the prawns' diet in November but disappeared completely from the diet between June and September. When seeds were not available, juvenile P. esculentus ate filamentous algae. Prawns less than 8 mm CL were not found with seeds in their foregut. There was no indication that prawns feed on seeds because of a shortage of other food items such as crustaceans or gastropods. Prawns studied in the laboratory removed seeds from the spathes and selected mature seeds. The seeds (each about 0.75 mg dry weight) had an energy content of 15.36 kJ g-1 dry weight. Seeds were found at densities of 456 m-2 in the seagrass beds. This study and other studies indicate that many species of juvenile penaeids incorporate vegetable material into their diet.