Effects of clove oil anaesthesia on European catfish (Silurus glanis L.)

The aim of the study was to investigate acute toxicity of clove oil for European catfish and, using values of haematological and biochemical profiles of blood and histological tissue examinations, to assess the effects of the fish exposure to that anaesthetic. Acute toxicity values of clove oil for European catfish found were 10minLC50 76.70 mg(.)l(-1); 10minLC0.1 49.60 mg(.)l(-1); 10minLC99.9 118.50 mg(.)l(-1); 96hLC50 18.40 mg(.)l(-1); 96hLC0.1 10.70 mg(.)l(-1); and 96hLC99.9 31.90 mg(.)l(-1). Individual phases of anaesthesia and recovery were determined. The 10-min exposure to clove oil at a concentration of 30 mg(.)l(-1) caused a significant ( p < 0.05) increase in the concentration of triacylglycerols ( TRIG), alanin aminotransferase ( ALT) and decreased ( p < 0.05) in mean corpuscular haemoglobin concentration ( MCHC) immediately after anaesthesia. The leukocyte counts were significantly ( p < 0.05) decreased 24 hours after anaesthesia. A significant ( p < 0.05) decrease of percentage distribution lymphocytes was found immediately after anaesthesia. On the other hand, percentage and absolute count of myeloid cells were increased. Increased percentage count of eosinophils outlasted 24 hours after anaesthesia, absolute counts of these cells were consistents with control. Histological examination showed capillary ectasia of gill filaments immediately after clove oil anaesthesia. Twenty-four hours after anaesthesia, no ectasia was observed. No histopathological changes were demonstrated in other tissues following anaesthesia. Results of the examinations suggest that the use of clove oil at a concentration of 30 mg(.)l(-1) does not cause irreversible damage in European catfish.