Goldan, O., National Center for Mariculture, P.O. Box 1212, Elat, Israel
Popper, D., National Center for Mariculture, P.O. Box 1212, Elat, Israel
Karplus, I., Department of Aquaculture, Agricultural Research Organization, P.O. Box 6, 50250 Bet-Dagan, Israel

The effects of particle size and frequency of feeding on survival, growth and growth depensation of juvenile gilthead sea bream were investigated in three separate experiments. In the first experiment the effects of dry food particle size and frequency of feeding were investigated with all treatments being equally supplemented with Artemia. Growth depensation, measured as the change in the coefficient of variation of mean weight (ΔCV), was affected by particle size but not by frequency of feeding. Frequency of feeding did, however, have a significant effect on growth rate. In the second experiment the effects of feeding brine shrimp, Artemia, as a supplemental feed were tested. Feeding continuously with brine shrimp resulted in a lower ΔCV than periodic feeding (ΔCV values of 15.6 vs. 21.8%, respectively). In the third experiment the effect of feeding Artemia as the sole source of food was tested. Continuous feeding resulted in a seven-fold higher ΔCV as compared to periodic feeding (ΔCV values of 24.6 vs. 3.6%, respectively). Competitive interactions between individuals of different size, and the differential attraction of fish to dry pellets and live food, are discussed as possible behavioral mechanisms underlying the results. Careful management of food administration (i.e. feeding frequency and particle size) could reduce the need for labor-intensive and stressful size-grading during nursing.