This work provides a comparative data of α-amylase activity in the gut extract of three Cyprinid species inhabiting Garma River (Basrah Governorate, Southern Iraq). Those species are bunny Barbus sharpeyi (herbivorous), common carp Cyprinus carpio (omnivorous), and shilik Aspius vorax (carnivorous). The study also investigate the discrepancy between the activity of the enzyme in common carp collected from Garma river with those reared in ponds. The specific activity of α-amylase has apparently been influenced by feeding habits of the three studied species. Values of α-amylase activity averaged 1.84 U mg -1 protein in the herbivorous bunny. It showed a significant (P<0.01) superiority to that of the omnivorous common carp (1.33 U mg -1 protein) which, in turn, showed a significant (P<0.01) superiority to that of the carnivorous shilik (0.76 U mg -1 protein). Omnivorous common carp which was collected from fish ponds showed a significantly (P<0.01) higher value of α-amylase specific activity which reached 1.92 U mg -1 protein when compared with the value recorded in common carp collected from Garma River which reached 1.33 U mg -1 protein.

This study was carried out for 60 day. A total number of 70 fish (Cyprinus carpio L.) with an average of 13.40±1.85 g and a length 11.07 ±1.27 cm were randomly divided into five treatments as a two tank treatment, similar to its contents of conventional ingredients (i.e., fishmeal, soybea soybean meal, corn, barley and wheat bran as well as vitamin mixture premix and carboxy methyle celloluse (CMC)). They differ in their content from food additives. They were commercially ready made in dietary T1 and T2 (Thepax 0.5, 1 gm/ kg), T3 and T4 (Labazyme 1, 2 gm/ kg) and control (0.0 gm/kg) of experimental diets. Data collected included fish weight and feed conversion ratio measured at the end of the study. The results found that the addition of food additives has significantly been affected by weight gain, specific growth rate and feed conversion ratio (P<0.05), with the best results obtained in fish food additives, pellets have been supplemented to Thepax 1 gm/ kg to enhance growth and immune responses.

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.

Laboratory experiments were conducted to compare the growth performance and feed efficiency of two groups, old (H1) and new (H2) of common carp Cyprinus carpio L. (97.37+0.33 g). Fishes of the H1 introduced to Iraq in 1982 and then their reproduction and farming began on a large scale, while fishes of the H2 was introduced to Iraq in 2009 by Inmaa Agricultural Enterprises Organization. H2 group indicated significantly (p<0.05) better performance in several studied parameters which included specific growth rate (SGR), feed conversion ratio (FCR), protein efficiency ratio (PER), protein productive value (PPV), total apparent digestibility and apparent digestibility of protein and carbohydrates. This group also recorded significant (p<0.05) lower feed satiation level and fat deposited in the body compared to the old group (H1). Results of the current experiment concluded that there is a clear higher efficiency of the group H2 in most studied growth and feed efficiency parameters, which indicates the possibility of obtaining higher productivity and better economic profits when used in farming activities.

The evaluation of raw and fermented water hyacinth Eichhornia crassipes (Mart.) Solms as dietary ingredient for young grass carp Ctenopharyngodon idella (Val, 1844) was carried out by adding 20% of each of the alternative ingredients separately to the control diet to completely compensate barley, a portion of wheat bran and 20% of fish meal. Results indicated that all growth and feed efficiency parameters among treatments were similar and there were no significant difference (p>0.05) in specific growth rate (SGR), food conversion ratio (FCR), protein efficiency ratio (PER) and protein productive value (PPV) of fish fed any of the diets. The diet containing fermented water hyacinth (WF) was found to be more efficiently utilized by fish and of highest digestibility values for all nutrients, which indicated that the digestibility was stimulated by incorporation of fermented water hyacinth. The raw water hyacinth diet (WR) produced significantly (p<0.05) highest satiation level associated with lowest digestible energy. Evacuation rate was not affected significantly (p>0.05) by the inclusion of raw or fermented water hyacinth to the diets. The protein, lipid and ash levels in carcass were higher in fishes fed the control diet (C). In conclusion, incorporation of raw or fermented water hyacinth up to 20% level was found to be suitable and there were no adverse effects on the growth and feed efficiency of experimental fishes.