Effect of stocking density and protein/fat ratio of the diet on growth of Dover sole (Solea solea)

250 soles (30g initial weight) were randomly placed in 12 experimental tanks at the Discizia’s aquaculture marine station. They were reared at 2 different stocking densities (2.3 and 1.3kg/m2 corresponding to 40% and 25% of the bottom surface area covered by fish) and fed on 2 diets with different protein/fat ratio (50% and 54% crude protein and 21% and 18% total lipid, respectively for diets A and B) with triplicate tanks per treatment. The trial lasted 120 days. Fish stocked at the lower density resulted in significantly higher weight gain than fish reared at 2.3 kg/m2 (29.0±7.3 g vs 20.3±8.0g; P<0.01) with a specific growth rate (SGR) of 0.54±0.09 and 0.42±0.13, respectively. Feed conversion rate (FCR) was improved at the lower density (1.8 vs 2.4, P<0.01). The chemical composition of the test diets significantly affected the growth performance of sole. Diet B led to a higher final weight (59.7 vs 50.8g; P<0.01) and better feed utilisation (FCR: 1.8 vs 2.4, P<0.01). These results confirm the necessity to ensure an adequate space for the growing sole and suggest the need for high protein diets to meet sole’s requirements.