Diet and weaning age affect the growth and condition of Dover sole (Solea solea L.)

The effect of diet type (frozen Artemia biomass and two inert diets: micro-bound [MB] and micro-extruded [ME]) and two weaning ages (early weaning and late weaning, 50 and 64 days after hatching, respectively) were studied in Solea solea larvae. The experiment lasted 56 and 42 days for early and late weaning, respectively. The mortality results showed the highest values for late weaning (39%) in the Artemia treatment. No significant differences in mortality were observed between the inert diets. The final dry weight values were higher for late weaning than for early weaning. At both weaning ages, fish receiving the same treatments had similar tendencies for dry weight and standard length. Fish fed with MB presented significantly higher dry weight and standard length, followed by ME, while the lowest values at both weaning ages were recorded for the Artemia treatment. Similar amounts of highly unsaturated fatty acid fractions among the inert diets were reflected by the absence of significant differences in the susceptibility to oxidation (thiobarbituric acid reactive substances testing); however, significant differences were found in carbohydrate, protein and lipid contents of whole-body homogenates for both early and late weaning. At the end of the experiment no significant differences in biochemical contents were observed between the two inert diets. The results of this study suggest that weaning starting on day 50 (early weaning), using a good quality inert diet, leads to higher survival, growth and fish condition.