No abstract

The e¡ects of dietary protein-energy levels on the growth rate, proximate composition and production were examined in Nile tilapia, Oreochromis niloticus, at two starting weights (22.9 and 39.8 g) reared in concrete ponds for 180 days. The highest weight gain (183.1g) was obtained with ¢sh fed a 30% protein and 10.5 kJ g À1 diet for the small initial size and 180.2 g for a diet containing 25% protein and 12.6 kJ g À1 for the large initial size. Dressed yields (edible mass) and ¢llets increased to 56.9% and 52.5% in ¢sh fed diet with 25% protein and 10.5 kJ g À1 at the initial size of 22.9 g, while ¢sh started at 39.8 g exhibited the best values (56.5% and 52.1%) when fed the 30% protein and 10.5 kJ g À1 diet. Proximate composition of soft tissue (wet weight basis) in small ¢sh was signi¢cantly in£uenced by dietary protein-energy levels. Protein was 26.1 AE 0.3% in ¢sh fed the high protein (30%) and low energy (10.5 kJ g À1 diet), while lipid content was 6.4 AE 0.3% at diet containing 20% protein and 14.7 kJ g À1 diet. Large initial size ¢sh fed the diet with 25% protein and14.7 kJ g À1 had the highest body protein (32.0 AE 0.4%) and lowest lipid content (2.2 AE 0.3%). Feed conversion ratio (FCR) and protein e⁄ciency ratio varied with di¡erent dietary proteinenergy levels and initial ¢sh sizes. Feed conversion ratio increased with increasing protein and decreasing energy level in the diet, and values in small ¢sh were higher than values in large ¢sh. Protein e⁄ciency ratio decreased with increasing dietary protein level and decreasing energy level. The maximum total production (7.6 tons feddan À1 ) was with dietary high protein (30%) and low energy (10.5 kJ g À1 ) for smallsized ¢sh, while large initial ¢sh had the highest production (3.7 tons feddan À1 ) when fed the 25% protein and 12.6 kJ g À1 diet energy. Starting with 22.9 g ¢sh was more advantageous than the initial size of 39.8 g for rearing Nile tilapia. Small ¢sh required a high-protein and low-energy diet, whereas large ¢sh required a low-protein and high-energy diet to achieve highest production.

Profenofos as an organophosphorus insecticide has been used in the agricultural countries as Egypt, may find its way to water system and adversely effect on aquatic life particularly fish. Nile tilapia, Oreochromis niloticus as a major fish species in River Nile and one of the major sources of protein for human beings in Egypt, and it can also be a source of threaten to human health. Transport profenofos directly to tilapia fish may affect their physiological status and then fish production. The mortality of profenofos toxicity was estimated on tilapia and LC50 was detected as 0.87 mg/l. Also fish were exposed to 1/2 LC50 for 96 hrs and to 1/10 LC50 for 28 days and lastly were left after the chronic toxicity for another 28 days as recovery period. The increase of blood glucose was accompanied with decrease in liver and muscles glycogen throughout the acute and chronic trail periods. Fish showed also highly significant decrease in serum total protein and globulin with increasing in albumin and A/G ratio. A sharp elevation in serum creatinine, urea and uric acid with decrease in serum total lipid, triglyceride and cholesterol were also recorded. Lastly gradual and sharp elevation in the levels of serum enzymes, S-AST, S-ALT and S-ALP was revealed in profenofos-exposed tilapia. Same behavior as S-AST and S-ALT were in liver transaminases (L-AST & L-ALT). Our study revealed adverse change of metabolism in tilapia due to profenofos exposure. This may inform about the dangerous use of profenofos and limitations should be managed.

N ile tilapia (Oreochromis niloticus) with an average weight of 40,0 g were reared with Sarotherodon galilaeus (initial weight of 5L0 g) and Clarias gariepinus (initial weight of 73.0 g) at three different combinations of monoculture, duoculture and polyculture systems. The fishes were stocked in seven earthen ponds with varied areas at a density of 4 fish/ m 2 during 210 days and fed on wheat bran. Some rearing ponds were fertilized weekly with a mixture of triple superphosphate and urea.At the end of the rearing period, the polyculture combination gave better growth rate and production for O.niloticus than in duoculture and monoculture systems. The average monthly increments were 21.lg and 29.0 g in ponds 2,3 (polyculture ponds), while in duoculture and monoculture, 18.7 g in pond 6 and 16.6 g in pond 4 were obtained. The specific growth rate and percentage weight gain reached their highest values for O.niloticus (0.85, 4.98 in pond 3 and 0.73, 3.64 in pond 2) using polyculture combination. On the other hand, O.niloticus showed better growth rate when cultured with Clarias gariepinus than with S.galilaeus. Its average weight was 131.0 g in pond 6 (O. niloticus with Clarias gariepinus and 128.5 g in pond 7 {O.niloticus with S.galilaeus).It was also observed that in the fertilized ponds, maximum growth in weight and production were recorded (0.379, 0.165 and 0.158 kg/m 2 for the three fish species respectively). In pond 3 (fertilized), the average final weight was 244.0 g for O.niloticus, 188.5 g for S. galilaeus and 332.0 g for Clarias gariepinus. The food conversion ratio has also the optimum value (3.14) for O.niloticus reared in polyculture system and fertilized pond.

T he effects of chronic exposure to sublethal doses of mercuric chloride (0.310, 0.155 and 0.078 mg L" 1) on growth rate, physiological parameters, chemical composition of tilapia species and properties of ponds water were studied for 180 days. Tilapia species (Oreockromis niloticus, Saroiherodon galilaeus and Oreochromis aureits) with an average initial size of 13 cm for total length and 50 g for body weight were stocked in fiberglass tanks (6 m 2 area of each) at a rate of 15 fish m* 2 (1:1:1) and fed on artificial diet containing 30 % protein. The physicochemical properties of ponds water were slightly varied with different mercury levels. The plankton organisms (phyto-and zooplankton) were gradually decreased with increasing the mercury concentration in fish ponds. The final body weight, daily weight gain and production of tilapia fish were significantly decreased with increasing the mercury level. The lowest values of these parameters (17L5g, 0.67g, 1.518 ton feddan" 1 for O. niloticus; 144g, 0.52g, L053 ton feddan" 1 for 5. galilaeus and 153.5 g, 0.56 g and 0.995 ton feddan * for O. aureus) were observed in the pond containing highest mercury level (0.310 mg/L). The other growth performance (specific growth rate, percentage weight gain and normalized biomass index), feed utilization (feed conversion ratio, protein efficiency ratio and protein productive value) and survival efficiency of tilapia were also affected with sublethal levels of mercury. The net returns and profitability of the reared fish were also decreased with increasing mercury concentration in ponds water. The lowest hematocrit (28.5, 29.0 166 Mohamed A, Sweilum and 30 %) and hemoglobin (5.5, 5.0 and 52 g/100 ml blood) of the three fish species were obtained from the pond containing 0.310 mg/L HgCh. At the same mercury levels, the serum protein of the three fishes decreased to 7.0, 6.6 and 6-5 g/100 ml serum, while serum glucose increased to 8L0, 79-0 and 78.5 mg/100 ml serum. The biochemical composition of fish muscles was also influenced with different sublethal levels of mercury, where the muscle protein and glycogen were slightly decreased and lipid increased with increasing the mercury level. The mercury residues in liver, gills and muscles of the reared fish were increased with increasing the mercury concentration in ponds water and its value in liver was higher than that in gills and muscles.