Comparison of tricaine methanesulphonate (MS222) and clove oil anaesthesiaeffects on the physiology of juvenile chinook salmon Oncorhynchus tshawytscha (Walbaum)

This study investigated the feasibility of using clove oil as an alternativ e to tricaine methanesulphonate as a fish anaesthetic, particularly in fish stress research. The physiological stress responses of juvenile chinook sa lmon Oncorhynchus tshawytscha (Walbaum) anaesthetized with either tricaine (50 mgL(-1)) or clove oil (20 p.p.m.) were compared using unanaesthetized f ish as controls. Haematocrit, serum cortisol and serum glucose concentratio ns, serum lysozyme activity and differential leucocyte counts were measured from blood samples collected before, during and upon recovery from anaesth esia and at specified intervals up to 72 h after recovery. Differences betw een the two anaesthetic groups were not significant for most of the physiol ogical traits measured. Serum lysozyme activity of control fish, however, w as significantly suppressed relative to the treated fish for 72 h after str ess. Clove oil may be a safe and cost-effective alternative to tricaine wit hout significantly affecting study results. Furthermore, clove oil may be m ore practical for field-based research, because a withdrawal period is unne cessary, and clove oil does not pose an environmental hazard.