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A laboratory experiment was carried out to investigate the effect of Thepax and Endo Vit. C as feed additives in the formulated diet on the growth performance of grass carp Ctenopharyngodon idella. The feed (30.11% crude protein) manufactured in the laboratory using raw local materials diet. Young grass carp (Average weight 3.36± 0.95 g) obtained from Aquaculture Unit ponds in Al-Hartha Station for Agricultural Researches, North Basrah. The fish were stocked in nine glass aquarium, three replicates for each treatment, of dimensions 60×40×30 cm provided with pumping aeration. The experimental diets included a control T1 (0% additives), T2 (1g Thepax/kg diet) and T3 (1g Endo Vit. C /kg diet) were used in feeding trail of current experiment. The experiment lasted for 57 days (from 29 Nov. to 24 Jan.) and fishes were fed six days a week using 5% of fish weight as feeding ratio. Results of current study reveals that grass carp fed on formulated feed supplemented with Endo vit. C having high growth performance (WG, DGR, RGR and SGR). The lowest Feed conversion ratio (2.511) was recorded in T3 this value was statistically significant (P≤0.05) with T2 while the highest value (2.767) was observed on the control. Protein efficiency ratio, feed intake and gross conversion efficiency were also recorded high values in T3, but control displayed superior values compared with Thepax treatment, which showed higher value of Relative feed intake compared to other two treatments.

A comparison was conducted for growth criteria of common carp, Cyprinus carpio larvae cultivated in earthen ponds and recirculation aquaculture system (RAS) depending on live foods (phytoplankton and zooplankton stimulated by buffalo fertilizers in earthen ponds, while the larvae cultivated in RAS were feed on Artemia larvae reproduced in vitro, in addition to manufactured pellets (38% crude protein) for common carp in both systems. Three 2500 m2 earthen ponds were cultivated for 90 days with larvae of initial weight 0.002 g at different numbers (40800 larvae for pond 1, 55600 larvae for pond 2 and 36400 larvae for pond 3). These larvae depend on natural food for 19 days, then fed on manufactured feed. Fishes were weighed every 19 days to change daily feed. Three replicates of RAS plastic tanks (100 letter capacity) cultivated for 90 days with 0.002 g larvae at a density of 2 larvae per one liter (160 larvae at each plastic tank). These larvae fed for 15 days to saturation (4 meals daily) with Artemia larvae and small Artemia, then fed on manufactured feed. Subsequently, fishes were weighed every 15 days to change daily feed. Larvae cultivated in earthen ponds recorded weight gain of 26.90 g, daily growth of 0.30 gday-1, relative growth of 1345000%, specific growth of 10.56 %day-1, feed conversion of 1.25 and survival rate of 13.16%. Larvae cultivated in RAS system recorded weight gain of 1.53 g, daily growth of 0.02 gday-1, relative growth of 76200%, specific growth of 7.37 %day-1, feed conversion of 2.82 and survival rate of 72.32%. Statistical analysis of results revealed significant differences (p>0.05) in all growth criteria for larvae cultivated in both systems. Final conclusion that earthen pond was better than RAS systems in producing fingerlings of common carp.

The early development of common carp (Cyprinus carpio L., 1758) was studied from fertilizing until juvenile stage. The series developmental staging was done using morphological characteristics. Results identified eight main periods of embryogenesis: zygote, morula, blastula, gastrula, neurella, segmentation, pharyngula and hatching period. Results also identified and described nine larval development stages: hatching larva stage, rudimentary - pectoral fin and gill arch stage, melanoid-eye with gas bladder emergence stage, one chamber gas bladder with yolk absorption stage, two chamber gas bladder stage, pelvic fin bud with dorsal fin formation stage, anal-caudal and pelvic fin formation stage, squamation stage and juvenile stage. Hatching occurred at 38h after egg fertilization. The fertilized egg was spherical, yellowish, transparent and 2.5 mm in diameter. The transition from larva to juvenile occurred in 30 days.

The current experiment was conducted in the Agricultural Research Station-Aquaculture Unit, College of Agriculture, University of Basrah from 27th June to 10th Nov 2020 in Al-Hartha District about 16 km northern-east of Basrah Governorate (30o65`64.6"N, 47o 74`79.5"E). Six earthen ponds (600 m3) were used to investigate the effect of three different initial weights of grass carp, Ctenopharyngodon idella [220.1-276.8 g (T1); 146.5-169.3 g (T2); 81.5-82.7 g (T3)]. Fishes were fed 3% daily using commercial pellets manufactured by Agricultural Consultant Office. The results of the current study indicated that T1 had better growth criteria (WI= 296.8 g, DGR= 2.53 g/day, SGR= 0.59%/day and FCR 5.23) compared with the other two treatments. There was a negative allometric pattern of growth (b less than 3) in the three treatments before and after the experiment. Statistical analysis of the results proved that there were significant differences (P≤0.05) in the modified condition factor (Kb) between the three treatments at the end of the experiment, while there were no significant differences (P>0.05) in the relative condition factor (Kn) and Fulton’s condition factor (K). It was concluded from the current experiment that the initial average weight of the grass carp must not be less than 250 g to achieved good results for fish culturist.

Effects of adding three dietary additives and their mixture to control diet (38% protein) on the growth performance and feed efficiency of young common carp Cyprinus carpio with an average weight of 16.16+0.09 g were assessed. These additives were probiotic (Saccharomyces cerevisiae yeast) (T1), amino acids (lysine and methionine) (T2), a mixture of exogenous enzymes (protease, cellulase, α-amylase, amyloglucosidase, pectinase, beta-glucanase, xylanase, phytase, lipase and beta mannanase) (T3), their mixture (T4) and control (T5). Inclusion of probiotic and exogenous enzymes showed significant (P<0.05) improvement in the growth performance and feed efficiency of the fishes compared with control and other additive diets. Otherwise, the inclusion of amino acids and the additive mixture did not show any significant (P>0.05) improvement compared with the control diet. Probiotic diet (T1) recorded greatest specific growth rate SGR (0.68%/day) and best feed conversion ratio FCR (2.84), followed by exogenous enzymes diet (0.57%/day and 3.44, respectively), while the SGR and FCR values for T2, T4 and control were decreased significantly (P<0.05). Probiotic and enzymes feed additives have proved significant enhancement of fish growth and feed efficiency.

In the present study, the morph-histological characterization of the brain development in common carp was studied in Basrah, Southern Iraq, by examining the several samples of eggs and larvae of Common carp Cyprinus carpio. The temperature of the water in incubators was 25 -27 ˚C and the incubation of eggs were carried out for 38 hour. Morphologically, neural stage was emerged after eight hours of incubation with continuation of epiboly processes Brain was progressively differentiated into three main parts namely forebrain, midbrain and hindbrain. Forebrain was differentiated into telencephalon and diencephalon. Optic primordial was appeared after 12 hours of fertilization in a form of evagination from both sides of the forebrain and slightly oval elongated and then characterized optic vesicle, then the lens was appeared. Hindbrain was clearly differentiated and neuromerse was marked after 22 hours of fertilization. Histologically, the brain at the age of 24 hours was composed of a mass of undifferentiated neuroectoderm, whilst at the age of 28 hours appeared more differentiated with clarity a cerebral hemisphere on both sides of the forebrain and it was a mass of undifferentiated neuron cells. Gradually, the brain parts were completed with a differentiation of several layers until the age of 20 days after hatching.