ABSTRACTn 84-day experiment was conducted to investigate the effects of two dietary protein levels 30 & 35% CP & three feeding frequencies 2, 3 & 4 times a day (8:0 and 11.0 h), (8.0, 11.0 and 14.0 h) and (8.0, 11.0, 14.0 and 17.0 h) on growth performance and feed utilization of the freshwater prawn, Macrobrachium rosenbergii with the Nile tilapia, Oreochromuis niloticus fry in a polyculture system. The experiment was conducted in small-scale hapas, 3.75 m -3 each in triplicates. Irrespective of polyculture system, prawn PL fed diet containing 35% CP 4 times a day had significant (P≤0.05) the highest final body weight (FBW), weight gain (WG), specific growth rate(SGR) and best feed conversion ratio (FCR) values among all treatments. Meanwhile, the Nile tilapia fed on diet containing 35% CP at 2 times/day recorded the highest significant FBW, WG, and best FCR among all treatments. The highest significant total biomass weight (kg hapa -1 ), and gain (kg hapa -1 ) and feed consumption (kg hapa -1 ) were obtained for prawn and tilapia feed the diet containing 35% protein. No significant differences (P≤0.05) were observed for SGR, FCR and S among all experimental hapas. The same trend was recorded for the different feeding frequencies.The highest values of the whole body CP, EE, ash and gross energy content were recorded for prawn fed on 30% diet at twice per day. No clear trend was observed for body composition of the Nile tilapia fry except for the highest lipid content (P ≤ 0.05) recorded for the fish fed on 30% CP diet 2 times per day. The findings of the current trials revealed that, feeding frequency has a great effect on growth performance and feed utilization efficiency of the freshwater prawn M. rosenbergii PL and the Nile tilapia fry. Feeding frequency 4 times per day for M. rosenbergii PL either 2 or 3 times per day for Nile tilapia fry is recommended under similar rearing condition to achieve best performance for both animals.

The present study addressed to investigate early, 25 days post hatching (dph) and late co-feeding time; 35 dph on European seabass (Dicentrarchus labrax) larvae. Initially, larvae were reared from the 5 th dph in six glass aquaria, and each aquarium contained 200 larvae.The results revealed higher, but no significant (P > 0.05) effect on larval final weight, weight gain, average daily gain and specific growth rate when larvae were co-feed at 35 dph. However, the highest survival rate was noticed then larvae were co-fed from 25 dph. Growth parameters showed significant (P < 0.05) effect on final gainsof both total and standard lengthswhen larvae were started co-feeding at 25 dph. The water quality showed no significant (P > 0.05) differences between treatments. However, significant (P < 0.05) effect was revealed on total culturable bacteria-and bacilli counts in water samples at 45 dph,when larvae were co-fed at 25 dph, but no significant (P > 0.05) effect was noticed on Staphylococcus counts at 45dph of larvae co-fed from 35 dph. Digestive enzymes analysis revealed that lipase activity was not significantly (P > 0.05) affected, however, a significant (P < 0.05) increase in amylase activity was revealed when larvae co-fed at 35 dph.