The quality of fish cultured using recycling units may differ from that of fish from outdoor farming units due to a range of deviating environmental determinants. This applies not only to flesh quality but also to morphological (processing) traits. This study evaluates processing yields of sibling fish cultured in two different farming units: (i) an outdoor pond aquaculture system with a flow-through regime (24.6 AE 0.2°C ), and (ii) indoor tanks using a recirculation aquaculture system (RAS; 26.0 AE 1.0°C). Clear differences were observed in the most important processing traits, i.e. skinned trunk and fillet yields, which were both significantly higher (P < 0.01) in RAS fish due to significantly smaller (P < 0.05) head weight in fish of the flow-through system. Skin represented a significantly higher (P < 0.01) proportion of total weight in both RAS males and females. The most obvious difference was in the deposited fat weight, which was significantly higher (P < 0.01) in RAS fish. Visceral fat deposits were significantly higher (P < 0.01) in females and ventral and dorsal fat deposits higher (P > 0.05) in males.

In order to limit the impact of industrial aquaculture activity on the environment and therefore, to be able to compete with recirculating aquaculture systems, pond based production systems must improve their sustainability by implementing innovative technical and technological solutions. The present study aims to identify the balance of phosphorus in two cyprinid polyculture ponds based production systems, by applying different rearing technologies and technical solutions. The design of present experiment consists in two ponds (PCP and CP-PP), stocked with common carp (CC), silver carp (SC), bighead carp (BC) and grass carp (GC), where different fish rearing technologies were applied. Also, in case of CP-PP, split-pond technique, together with a particular hydraulic regime was used. The phosphorus input through administrated feed was 165% higher in the case of PCP, compared to the CP-PP. The results obtained by using Sankey diagram revealed higher percentages of phosphorus accumulation in water (> 1000%) and sediments (> 15%), in the case of PCP pond, compared to the CP-PP pond. However, higher percentages of phosphorus accumulation in fish biomass were registered at PCP pond (>8% in CC, 500% in SC, 150% in BC and >118% in GC). As a conclusion, by applying split-pond technique, together with a particular hydraulic regime and fish rearing technology, phosphorus footprint of cyprinid polyculture ponds can be reduced, by decreasing the concentration of this element in output water and sediments.

This study aims to identify proper solutions that can improve the sustainability of cyprinids pond aquaculture in terms of nitrogen releases to the environment. Therefore, two experimental variants, based on polyculture, respectively integrated multi-trophic aquaculture (IMTA) concept were tested, as follows: PCP – polyculture of common carp (CC) + grass carp (GC) + bighead carp (BC) + silver carp (SC); CP-PP – net divided pond with CC monoculture in CP part and CC+GC+BC+SC polyculture in PP part. In order to determine the nitrogen accumulation at the pond level, samples of water, sediments, fish meat and reed were analyzed. The results indicate that the highest nitrogen compounds concentrations in pond water were registered at CP part of CP-PP pond. However, the nitrogen concentration in pond effluents was significant higher in case of CP-PP pond, compared with PCP pond. The nitrogen compounds concentration of sediments registered the highest values in the ponds outlet area. Also, CP-PP pond recorded higher nitrogen concentration in sediments, compared with PCP pond. The CC registered the highest nitrogen compounds concentration in case of PP pond area, followed by CP pond area and PCP pond. Not significant correlation was found between reed and pond water/ fish meat/ sediments in terms of nitrogen compounds concentration. It can be concluded that the CP-PP pond feeding management, together with the tested technical solution (pond dividing) generated better water conditioning performances.