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¹ Karnataka Veterinary, Animal and Fisheries Sciences University, Department of Aquaculture, College of Fisheries, Mangalore, India
² Birds Krishi Vigyan Kendra, Tukkanatti, Gokak, Belgaum, India DOI : 10.4194/1303-2712-v11_4_11 Viewed : 4392 - Downloaded : 4910 Two field experiments, each of 98-day duration, were conducted in outdoor mud- bottomed cement tanks, employing common carp (Cyprinus carpio) fry and fingerlings, with a view to study the effect of nutrient inputs (feed, manure and their combination) on different life stages of the fish. The treatments consisted of control (C), only feed (F), only manure (M) and manure plus feed (M+F). Poultry manure was applied in split doses to tanks of manure treatments (M and M+F). Fry (Experiment one) and fingerlings (Experiment two) of average weight 0.67 g and 3.2 g respectively, were stocked seven days after the initial manure application at 4 individuals/m². Fish in F and M+F treatments were provided a fish meal based pelleted diet once daily in the morning at 5% of body weight. The most dominant genera of phytoplankton encountered were Microcystis, Anabaena and Microspora, while among the zooplankton, Keratella and Nauplii dominated. M+F treatment had the highest plankton biomass (P<0.05). Significant (P<0.05) variation in both phyto and zooplankton dry weight was recorded with respect to the study period. Both feeding and manuring, individually and in combination, significantly improved (P<0.05) the growth of fish. The highest specific growth rate, final fish weight, and gross production were recorded in M+F treatment in both the experiments. The difference in survival among the control and treatments was not significant in experiment one (P>0.05), whereas F and M+F treatments recorded lower survival (P<0.05) in experiment two. Fish production was comparable under feed (F) and manure (M) treatments (P>0.05) in experiment one, but was significantly (P<0.05) different in experiment two. The increment in gross fish production over the control was 103.22 and 119.99% in feed, 77.30 and 59.44% in manure and 162.34 and 175.08% in M+F treatments of the two experiments respectively. Carcass protein, fat and ash contents were significantly (P<0.05) higher in the three treatments as compared to the control. The different digestive enzymes recorded higher values in fish from the three treatments than those of the control. Keywords : Natural food, poultry manure, life stage, carcass composition, digestive enzymes