Oxygen consumption, ventilation frequency and cytochrome c oxidase activity in blue cod (Parapercis colias) exposed to hydrogen sulphide or isoeugenol

The effects of hydrogen sulphide (H2S) and isoeugenol exposure on activity, oxygen consumption (VO2), ventilation frequency (Vf) and cytochrome c oxidase activity in a teleost fish are reported. In H2S (200 µM Na2S) exposed animals VO2 and Vf decreased significantly (both to 40% of resting) after 30 min, concurrent with a loss of equilibrium and narcosis. Post-flushing, VO2 increased to resting values, but Vf remained depressed (P < 0.05) until 30 min of recovery. Subsequently, equilibrium and mobility were regained accompanied by increases in VO2 (66%) and Vf (15%) between 60–70 min of recovery. Isoeugenol (0.011 g L− 1) exposed fish reached stage 4–5 of anaesthesia accompanied by decreases (P < 0.05) in VO2 (64%) and Vf (38%) by 35 min. Post-flushing, VO2 and Vf recovered to resting values, followed by a rise (P < 0.05) in VO2 (45%) and Vf (25%). Overall, VO2 in relation to the resting rate was reduced in isoeugenol treated animals. Conversely, VO2 was increased (P < 0.05) relative to the resting rate in H2S exposed fish. 20 and 200 µM Na2S reduced cytochrome c oxidase activity (P < 0.05) in skeletal muscle and gill lamellae by between 69 and 97%, while isoeugenol had no effect in any tissue.