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

Abstract

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