Abstract
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.
Highlights
Anaesthesia, euthanasia and sedation of both wild and captive fish are common requirements in aquaculture and fisheries research around the world
The aim of the present study was to investigate acute toxicity of clove oil in European catfish and, on the basis of haematological indices, biochemical blood profile values and histological examinations, to assess the changes in the organism of European catfish induced by the anaesthetic
The 96-h LC50 test: Experimental fish were exposed to concentrations 5, 10, 16, 18, 30 and 40 mg·l-1 clove oil dissolved in diluting water, and controls were placed in diluting water with no tested substance added
Summary
Anaesthesia, euthanasia and sedation of both wild and captive fish are common requirements in aquaculture and fisheries research around the world. These clinical techniques facilitate a wide variety of activities such as sorting, grading, transportation, tagging, gamete collections, health monitoring, weight/length measurements, blood sampling and invasive surgery to name a few. Effects on clove oil on commercially produced fish are studied in a project regarding the application of principles of pharmacovigilance in aquaculture in the Czech Republic. In the second stage of the project, effects of clove oil on rainbow trout (Velí‰ek et al 2005a) and common carp (Velí‰ek et al 2005b) were studied. The aim of the present study was to investigate acute toxicity of clove oil in European catfish and, on the basis of haematological indices, biochemical blood profile values and histological examinations, to assess the changes in the organism of European catfish induced by the anaesthetic
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