Size-relative Effectiveness of Clove Oil as an Anaesthetic for Rainbow Trout (Oncorhynchus mykiss Walbaum, 1792) and Goldfish (Carassius auratus Linnaeus, 1758)

Abstract

The purpose of this work was to investigate the size relative effectiveness of clove oil as an anaesthetic for rainbow trout and goldfish In total 128 rainbow trout (Oncorhynchus mykiss) (two groups of 20 23 and 30 33 cm mean fork length) and 160 goldfish (Carassius auratus) (four size groups of 1 5 2 5 5 7 11 15 and 20 25 cm) were anaesthetized at different clove oil concentrations of 50 100 150 mg l (1) for trouts and 75 100 150 mg l (1) for goldfish Rainbow trout exhibited total loss of balance and no response to external stimuli with shorter induction time as dosage increased (120 5 s 64 4 s and 44 3 s, respectively) Goldfish exhibited total loss of balance and no response to external stimuli after induction time that varied with dosage used and body size of fish The small fish (1 5 7 cm) exhibited shorter induction time which ranged from 84 28 Sat 75 mg l (1) clove oil to 41 14 s at 150 mg l (1) clove oil The larger fish had a longer induction time inversely related to the dosage Recovery time was longer than induction time in both species Both species recovered within 6 mm after anaesthesia at 150 mg l (1) clove oil Clove oil did not produce marked changes (P < 0 05) in the physiological indicators of goldfish compared to the control However marked changes (P < 0 05) were exhibited in the haematocrit of treated rainbow trout that also exhibited hyperkalaemia and hyperglycaemia (P > 0 05) For both fish species, clove oil was effective, producing minimum stress and zero mortalities, and can be recommended as an effective anaesthetic