A preliminary study to determine optimal feed rations for Cyprinus carpio L. × Carassius auratus L. hybrids reared in cages in spent cooling water

This study was conducted to investigate the effects of feeding rations on growth, feed utilization, and proximate composition of Cyprinus carpio × Carassius auratus hybrids reared in cages located in power station cooling waters. The study was conducted at the Fisheries Experimental Station of the Department Aquaculture of West Pomeranian University of Technology in Szczecin located at the Dolna Odra Power Plant. The studies used the carp feed Classic (30.6% protein, 8.8% lipid, 47.5% carbohydrate, and 18.1 MJ kg⁻¹ gross energy) in the following rations: 0.8%, 1.2%, 1.6%, 2.0%, and 2.4% of fish metabolic weight. Each of the variants were tested for 140 days in triplicate at a density of 150 fish per cage. During the experiment, the water temperature ranged from17.1 to 34.3°C, pH was 7.5-9.0, and oxygen was 2.8-12.6 mg dm⁻³. At the end of the study, the mean individual body weights of the hybrids ranged from 150 to 430 g and the FCR was from 1.44 to 2.32. The optimal piecewise regression model rations were 1.4% of metabolic body weight.