The anaesthetic effect of clove oil on common carp, Cyprinus carpio L

Anaesthetics play an important role in both fisheries research and aquaculture, being used to facilitate various handling procedures, such as weighing, sorting, collection of spawning material, tagging, or veterinary treatment (Summerfelt and Smith 1990, Kazuñ, Siwicki 2001). Anaesthetics act with various intensity, driving fish into general anaesthesia, resulting in loss of consciousness, inhibition of reflex activity, and reduced skeletal muscle tone (McFarland 1960). Regardless of the agent, the process of anaesthesia in fish, develops in a similar way and runs in a progressive pattern (McFarland 1959). Overdosing an anaesthetic or retaining the fish in an anaesthetic bath for too long leads to the fading of ventilation, hypoxia, and finally—respiratory and cardiac collapse (Tytler and Hawkins 1981). The fading of ventilation is an important warning sign suggesting that the exposure should be terminated (Hajek and K3yszejko 2004, Dziaman et al. 2005). The most widely used anaesthetics include MS-222 (tricaine methanesulphonate), benzocaine, etomidate, metomidate, 2-phenoxyethanol, quinaldine, and quinaldine sulphate. Also clove oil has recently been pointed out as a potential fish anaesthetic. Clove oil is derived from the stem, leaves, and buds of the clove tree, Eugenia caryophyllata, and it contains the active ingredient eugenol. It has been reported to be effective on several species of fish (Soto and Burhanuddin 1995, Anderson et al. 1997, Munday and Wilson 1997, Keene et al. 1998, Peake 1998, Iversen et al. 2003, Wagner et al. 2003). Its main advantages lie in its low cost, and its relative safety to both fish and humans (Keene et al. 1998). There has been only one attempt to study the effects of clove oil on common carp, performed by Velíšek at al. 2005. Those authors investigated acute toxicity (LC) of clove oil using 10-min and 96-h exposure time with a survival as the main criterion. The objective of the presently reported study was to establish the lowest effective conACTA ICHTHYOLOGICA ET PISCATORIA (2006) 36 (2): 93–97