Clove oil has become a popular fish anaesthetic for invasive fisheries research procedures, but
few studies have examined the use of low concentrations of clove oil to achieve sedation for
aquaculture procedures such as fish handling and transport. In this study, we used largemouth bass
as a model species to examine the behavioral and physiological responses of fish to a gradation of
clove oil concentrations (0 to 20 mg l1) while exposed to truck transport. Concentrations of clove
oil ranging from ~5 to 9 mg l1 elicited a sedative effect resulting in loss of reactivity and reduced
cardiac output while maintaining equilibrium. Fish sedated by 5 to 9 mg l1 clove oil achieved that
level of anaesthetization rapidly and recovered behaviorally more quickly than at higher
concentrations. During transportation, videography revealed that fish in deep sedation (stage 2induction) experienced the least opportunity for physical damage from the tank or conspecifics and
had reduced activity relative to other concentrations. Cardiovascular assessments indicated that
when exposed to clove oil of any concentration, cardiac output and heart rate rose following an
initial bradycardia. Fish exposed to low levels of clove oil recovered rapidly when returned to fresh
water, but those exposed to higher concentrations (usually stage 4 or 5 induction) exhibited
protracted cardiovascular recovery. Recovery occurred more rapidly for fish that were exposed to
stage 2 anaesthesia than nonanaesthetized controls. Low levels of clove oil (5 to 9 mg l1) yielded
rapid induction and maintenance of stage 2 anaesthesia in subadult largemouth bass and was
effective for mitigating the effects of fish transport stress. The results from this study could be
useful for aquaculturists and other handling related husbandry practices that require sedation of
fish.