Feeding habits of juvenile stages of Sparus auratus L., Dicentrarchus labrax L. and Mugilidae in a brackish embayment of the Po River Delta

Abstract

The feeding habits of juvenile stages of gilthead ( Sparus auratus L.), sea bass ( Dicentrarchus labrax L.) and three species of grey mullets ( Liza ramada Risso, Liza aurata Risso and Liza saliens Risso) in a Po Delta embayment (Sacca di Scardovari) were studied. Samples were taken over two years, 1977 (from April to June) and 1978 (from February to December). The stomach contents of a total of 858 individuals were examined. The feeding habits of fish fry of the five species did not differ noticeably in the smaller-sized stages (standard length (SL) < 30 mm), which are carnivorous with a prevalently planktophagous diet; Cirripedia nauplii, Copepoda and Polychaeta larvae are the most important food items. The food preferences tend to change when the size is over a SL of 30 mm; gilthead feed preferentially on macrobenthos (Polychaeta and Amphipoda) and macrophyte detritus, and sea bass on macroplankton (Mysidacea, Decapoda larvae and fish larvae); grey mullets have a mixed diet including benthic microalgae, sand and silt, zoobenthos and zooplankton organisms. The diet of young grey mullets is furthermore characterized by the presence of adult insects. The composition of the stomach contents of the different fry species was also analyzed in relation to the composition of some zooplankton and zoobenthos taxocoenoses in the embayment.