Stress produced by therapeutic copper sulphate concentrations on Carassius auratus (Pisces, Cyprinidae)

Abstract

To evaluate if therapeutic treatment with copper sulfate produced stress on juvenile Carassius auratus (Linnaeus, 1758), fish were exposed to copper bath during 30 min, copper concentrations were 0.5 and 1.0 mg Cu2+/l, named C1 and C2, respectively. Control groups were included in each experiment. Fish stress was measured by challenge test of residual dissolved oxygen (RDO, mg O2/l) in small (Class A: 1.67 ± 0.12 g) and large carps (Class B: 2.57 ± 0.18 g). Results show that C2 stressed small carp. Obtained RDO in those carps was 35.7% higher than control fish and 35.5% higher than fish exposed to C1 (P < 0.05). Oxygen consumption was 39.5% more elevated than control group and 52.6% higher than C1 (P < 0.05). Both weight classes were compared; RDO-Class A was similar to Class B in C1, and in C2 was 42.9% higher than this one. The RDO was 32.7% smaller in Class A than in Class B in C1 but 39.5% higher than this in C2. The oxygen extraction efficiency (90%) was similar in all groups. Results obtained in this study, considering maintenance and feeding (36% protein), are important to cultivate C. auratus juveniles. In therapeutic treatments with copper sulphate, we recommend the procedure used in this work in order to avoid masking the copper noxious effect.