Observations of carbon-nitrogen manipulation and periphyton growth stimulation on fish farming in an integrated intensive-extensive aquaculture system
The results of observations of intensive sturgeon production integrated with an extensive earthen fish pond are described. The main objective of the study was to show how technological modifications applied to enhance nitrogen assimilation in ponds and nutrient retention in aquaculture products influenced fish production. Each of two integrated systems, A and B, consisted of four intensive fish tanks stocked with sturgeon and one extensive carp pond stocked with carp (Cyprinus carpio L.), silver carp (Hypophthalmichthys molitrix (Val.)) and common nase (Chondrostoma nasus L.). The fish tanks were supplied with water from the extensive pond and the effluent from the tanks was discharged into the same pond, which acted as a biological filter for fish production. System B pond was supplemented with carbohydrates (methanol) and plastic substrates for periphyton development that were installed to increase nutrient utilization. The results of the observations showed better water quality and higher fish production in pond B, but no differences were noted in sturgeon growth performance in system A. The combination of these modifications appeared to be an efficient way of increasing nutrient retention and improving water quality.