CARP FISH REARING IN AUTOCHTHONOUS MIXED POLYCULTURE (CYPRINUS CARPIO, L., ARISTICHTHYS NOBILIS RICH. AND CTENOPHARYNGODON IDELLA VAL.)

NIKOLOVA, L., L. HADJINIKOLOVA, K. DOCHIN, D. TERZIYSKI, R. ATANASOVA, A. STOEVA, G. GROZEV and E. PASKALEVA, 2008. Carp fish rearing in autochthonous mixed polyculture (Cyprinus carpio, L., Aristichthys nobilis Rich. and Ctenopharyngodon idella Val.). Bulg. J. Agric. Sci., 14: 139-144 For the needs of organic fish farming at the Institute of Fisheries and Aquaculture-Plovdiv, the levels of natural fish productivity of carp fish, reared in polyculture, based on a natural nutritive basis (an “autochthonous polyculture”) have been investigated. The experiment has been carried out in five fish ponds with a total area of 1.47 ha (two fish ponds – with 3000 kg.ha -1 of organic manure applied), three fish ponds (no organic manure applied). Before supplying with water, 300 kg.ha -1 of quicklime has been applied, and during the vegetation period – an additional quantity of 150 kg.ha -1 . The quantity of the organic manure and quicklime used has been conformed to the requirements for organic fish farming. The polyculture structure has been the following: one-year old carp - 500 pcs.ha -1 ; one-year old bighead carp - 300 pcs.ha -1 and two-years old grass carp - 100 pcs.ha -1 , with an average single fish weight (ASFW) in the fish-stocking of ponds, respectively – 0.071; 0.034 and 0.578 kg. During the vegetation period the quality of water has been within the technological standards. The ponds have ensured a good natural nutritive basis. From the experimental ponds max 645 kg.ha -1 of yield and 545 kg.ha -1 of gain have been obtained, when organic manure has been applied and max 537 kg.ha -1 of yield and 437 kg.ha -1 of gain, when no organic manure has been applied. The maximum carp gain has reached up to 241 kg.ha -1 (final ASFW of 0.555 kg); of the bighead carp – 200 kg.ha -1 (final ASFW of 0.699 kg); of the grass carp – 124 kg.ha -1 (final ASFW of 1.837 kg). At the conditions of the experiment, the two-summer old grass carp has exercised a reducing effect upon macrophytes growth.