Influence of Cadmium on the Respiratory Function of the Grass Carp Ctenopharyngodon idella

The effect of 96 h exposure tosublethal cadmium concentrations on oxygen consumptionrate (VO2 mg h-1) and oxygen extractionefficiency (OEE′ %) was determined in juvenile Ctenopharyngodon idella acclimated to 26, 29 and 32 °C for at least two weeks. The relationshipsamong the physiological rates (VO2 andOEE′, body weight and temperature, were fittedby second order polynomial models; the responsesurfaces generated allowed the evaluation of stressinduced by the interaction of those variables. BothVO2 and OEE′ invariably increased astemperature increased. In small animals kept in 0.5 mgCd L-1, the VO2 increase was compensated bya proportional increase in OEE′, whereas inlarger fishes (>1 g) no compensatory response wasobserved. Both small and large fishes were unable tocompensate for a higher VO2 when exposed tohigher cadmium concentration. It is concluded thatOEE′ in young fish is an early response of stressdue to sublethal cadmium exposure.