Prey selectivity of naked-head large-eye bream (Gymnocranius griseus, Temminck & Schlegel 1844) larvae on natural plankton at first feeding.

摘要

The study was conducted to determine the feeding preference of Gymnocranius griseus larvae at first feeding. Eggs of G. griseus were collected from broodstock. Batches of 100 fertilized eggs were transferred into 1 litre polycarbonate containers in triplicate filled with <=2 micro m seawater. Feeding experiments on first-feeding larvae were carried out 60-72 h after hatching and were repeated seven times between 15 and 29 August 2006. The six containers, 1 litre, were maintained at 24.0-25.6 degrees C during the feeding experiments and aeration was <60 ml/min. It was observed that at first feeding G. griseus larvae fed on nano-sized protozoa (flagellates and ciliates), micro-sized protozoa (flagellates, ciliates and tintinnids), bivalve larvae, copepod nauplii and diatoms, except for nano-tintinnids; plankton size averaged 10.5-64.3 micro m, except for diatoms. The feeding rates of G. griseus larvae increased with initial density of prey plankton in the experimental containers. Feeding rates on diatoms at 571.1-78 042.4 cells/larvae/h were the highest for the prey plankton groups, followed by microflagellates at 151.6-2772.7 cells/larva/h. On the other hand, feeding of G. griseus on microflagellates, microciliates, microtintinnids, bivalve larvae and copepod nauplii tended to be positive. Positive feeding on diatoms was demonstrated in four of seven trials. It is suggested that G. griseus larvae, at first feeding, prefer microsized plankton (20-60 micro m) to nanosized plankton (10-20 micro m).