AACL Bioflux, 2015, Volume 8, Issue 5. http://www.bioflux.com.ro/aacl 632 AACL BI OFLUX Aquaculture, Aquarium, Conservation & Legislation International Journal of the Bioflux Society The influence of stocking density on growth performance, feed intake and production of common carp, Cyprinus carpio L., at one summer of age, in ponds aquaculture systems Lucian Oprea, Mihai C. Mocanu, Tiberiu Vanghelie, Petronela G. Sandu, Lorena Dediu ” Dunărea de Jos” University of Galati, Faculty of Food Science and Engineering, Galati, Romania. Corresponding author: L. Dediu, lorena.dediu@ugal.ro Abstract . The paper presents some aspects regarding the influence of stocking density on common carp ( Cyprinus carpio) fry and fingerlins, fed with extruded and expanded pellets. The experiment covered a 150 day-period, and was made in four small breeding units, type pond, 6000 m 2 each. Two kind of stocking density variants were compared, with repetition: V1, with 30000 fish ha -1 (30 kg ha -1 ) and V2, with 15000 fish ha -1 (15 kg ha -1 ), respectively. The growth parameters (FBG, GR, SGR, FCR) at the end of the experiment, revealed that the mean biomass gain in V1 was 4295 kg ha -1 compared to 2275 kg ha -1 in V2. This was nearly perfectly correlated with the stocking density. The mean growth rate (GR) of fish biomass varied in a similar way, from 28.63 kg day -1 in V1 to 15.17 kg day -1 in V2. The mean specific growth rate (SGR) of fish biomass was 3.31% day -1 in V1 and 3.35% day -1 in V2. This shows that the fish growth was very good. The mean feed conversion ratio (FCR) was 1.41 kg of pellets/kg weight gain in V1 and 1.33 kg of pellets/kg weight gain in V2. The parameters of fish growth performance showed that variation in stocking density did not negatively influence the fish production, the common carp having a very good growth rate. An increase of fish biomass is possible if pellets with a moderate level of crude protein (30%) are used. Key Words: common carp juveniles, extruded/expanded pellets, water quality, feed efficiency. Introduction . Common carp ( Cyprinus carpio L.) is the oldest cultured and the most domesticated fish species of the world (Flajšhans & Hulata 2007; Lehoczky et al 2005; Balon 1995). In Central–Eastern Europe, Romania is one of the traditional common carp and chinese carp producing countries, with more then 10000 metric tons year -1 ( FAO 2015). Stocking density is an important factor to be considered in fish aquaculture. It is widely accepted that inadequate stocking density is one of the main factors that restricts the growth and survival of fish species in different culture systems. Growth performance is probably one of the most well studied physiological parameters related to aquaculture research (De las Heras et al 2015). Survival and production of fry and fingerlings in ponds system depend on stocking density also, type and quality of fertilizers and supplementary feeds (Chakraborty & Mirza 2007; Drew et al 2007). High biomass could activate stress response affecting negatively the final fish production, while low stocking densities could suppose, due to an inadequate use of space, higher production costs and lower profitability for the industry. Moreover, under intensive fish culture systems, high stocking densities together with insufficient water renovation in the rearing units could decrease water quality, compromising the growth of fish (Pickering 1990; Ruane et al 2002; De las Heras et al 2015). This study aimed to evaluate the effect of different stocking densities on common carp fry and juveniles growth performance and feed efficiency.