Influence of salinity on energy metabolism in juvenile turbot, Psetta maxima (L.)

Oxygen consumption (OC) was measured for 24h in juvenile turbot, Psetta maxima (L.) using flow-through respirometry to examine the influence of salinity on energy metabolism. Turbot [164g mean initial body weight (BW)] were reared at 16.5 +/- 0.2 degrees C and three different salinities (10, 20, 30g L-1). Digestible and metabolizable energy requirements for maintenance (DEm; MEm) as well as the respective efficiencies of energy utilization for growth (k(g (DE)); k(g (ME))) were identified using different feeding levels (0.3, 0.6, 0.9gkg(-1) metabolic BW) and applying linear regression analysis. We found that nutrient and energy digestibilities decrease with an increasing salinity. DEm and MEm were 14.9-20.2 and 13.3-18.3kJ kg(-0.8) day(-1) and k(g (DE)) and k(g (ME)) 0.82-0.87 and 0.87-0.91, respectively. No differences were observed in DEm, MEm, k(g (DE)) and k(g (ME)) between salinities, although these parameters were low at a high salinity (30g L-1). Turbot showed the most favourable combination of DEm and k(g (DE)) (MEm and k(g (ME))) at a salinity of 20g L-1 and at 30g L-1 growth and energy utilization were reduced at high energy intake. However, energy requirements for iono- and osmoregulation were small.