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 individu als) of European sea bass (Dicentrarchus labrax) were measured at combinati ons of the following factors: temperature (10, 15, 20 and 25 degrees C), ox ygenation 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 t he metabolic range accessible. Osmoregulatory costs are linked to metabolic activity through ventilation. This relationship was highlighted by the obs erved interaction between environmental salinity and temperature. We were, however, unable to detect interactions between salinity and routine metabol ic rate, or between salinity and oxygenation level. In order to delineate m on precisely the restrictions imposed by water oxygenation on fish metaboli c performance we determined the limiting oxygen concentration curves at eac h experimental temperature. We followed up by modelling the bass active met abolic rate (AMR) and metabolic scope (MS) as functions of both ambient tem perature and oxygenation. These mathematical models allowed the characteris ation of the controlling and limiting effects of water temperature and oxyg en content on the metabolic capacity of the species. Thus, AMR at 10, 15 an d 20 degrees C were estimated at 65, 160 and 360 mg O-2 kg(-1) h(-1), respe ctively. 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 1 0 and 20 degrees C, but diminished at higher temperatures. The present stud y contributes to our current understanding of the influences of environment al factors on the metabolism of sea bass and provides a bioenergetic basis for a study of how environmental constraints govern the spatial and tempora l distribution pattern of this species. (C) 1999 Elsevier Science B.V. All rights reserved.