Influence of temperature, oxygen and salinity on the metabolism of the European sea bass

Standard (SMR) and routine (RMR) metabolic rates of groups (4 to 5 individuals) of European sea bass (Dicentrarchus labrax) were measured at combinations of the following factors: temperature (10, 15, 20 and 25 degrees C), oxygenation level (air saturation to 1.5 mg dm(-3)) and salinity (30, 20, 10 and 5 parts per thousand). The influence of these environmental conditions on fish metabolic demand was then analysed through ANOVA. At 10, 15, 20 and 25 degrees C, standard metabolic rates were 36, 65, 89, and 91 mg O-2 kg(-1) h(-1), respectively, while routine oxygen consumptions covered most of the metabolic range accessible. Osmoregulatory costs are linked to metabolic activity through ventilation. This relationship was highlighted by the observed interaction between environmental salinity and temperature. We were, however, unable to detect interactions between salinity and routine metabolic rate, or between salinity and oxygenation level. In order to delineate mon precisely the restrictions imposed by water oxygenation on fish metabolic performance we determined the limiting oxygen concentration curves at each experimental temperature. We followed up by modelling the bass active metabolic rate (AMR) and metabolic scope (MS) as functions of both ambient temperature and oxygenation. These mathematical models allowed the characterisation of the controlling and limiting effects of water temperature and oxygen content on the metabolic capacity of the species. Thus, AMR at 10, 15 and 20 degrees C were estimated at 65, 160 and 360 mg O-2 kg(-1) h(-1), respectively. However, at higher temperature (25 degrees C) AMR dropped slightly (to 340 mg O-2 kg(-1) h(-1)). Bass MS increased by a factor of 9 between 10 and 20 degrees C, but diminished at higher temperatures. The present study contributes to our current understanding of the influences of environmental factors on the metabolism of sea bass and provides a bioenergetic basis for a study of how environmental constraints govern the spatial and temporal distribution pattern of this species. (C) 1999 Elsevier Science B.V. All rights reserved.