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.
Abbrevitions: ASFW - average single fish weight; K1+ - two-summer old carp; T1+ - two-summer old bighead carp; A2+ - three-summer old grass carp