Effects of clove oil and MS-222 on blood hormone profiles in rainbow trout Oncorhynchus mykiss, Walbaum

Abstract

Clove oil has been demonstrated to be an e¡ective, inexpensive anaesthetic and euthanizing agent for a number of ¢sh species, including rainbow trout, used in aquaculture and ¢sheries research. However, the potential for clove oil to cause perturbations in important plasma hormone concentrations has not been investigated. The e¡ect of anaesthesia and euthanasia in trout with eugenol (the active ingredient in clove oil) on plasma cortisol, glucose, growth hormone (GH) and two thyroid hormones [tri-iodothyronine (T 3 ) and thyroxine (T 4 )] was compared with tricaine methanesulfonate (MS-222) anaesthesia, and stunning by cranial concussion in two experiments. E¡ects on blood chemistry were di¡erent when comparing the particular anaesthetic method being used. Stunning ¢sh signi¢cantly increased plasma cortisol and glucose levels (both Po0.05), while euthanizing ¢sh using either clove oil or MS-222 had no e¡ect on these hormone levels. In contrast, the levels of GH,T 3 and T 4 hormones were un-a¡ected regardless of whether ¢sh were euthanized by stunning, MS-222 or clove oil. Variation in e¡ects between hormones were observed using clove oil eugenol. In ¢sh sampled 10 min after anaesthetizing with 150 mg L À1 of eugenol, cortisol levels were sig-ni¢cantly decreased (Po0.03), while there were no di¡erences in either glucose or GH levels. Tri-iodothyronine and T 4 also showed signi¢cantly elevated levels (Po0.05) after 10-min exposure to eugenol. These results highlight the importance of investigat-ing the potential e¡ects of any new anaesthetic or euthanizing compounds on blood plasma parameters, prior to using them in a research setting, or when comparing results to other studies which have utilized alternative anaesthetic compounds.

Effects of clove oil anaesthesia on common carp (Cyprinus carpio L.)

“…Increased blood plasma glucose level after anaesthesia indicates that the procedure caused some stress in the carp. These findings are in accord with results of Holloway et al (2004) and Velisek et al (2005) who also detected increase of glucose concentration in rainbow trout (Oncorhynchus mykiss) following clove oil anaesthesia. On the other hand, Iverzen et al (2003) found no change in the concentration of glucose in Atlantic salmon (Salmo salar) following clove oil anaesthesia.…”

Effects of Clove Oil Anaesthesia on Rainbow Trout (Oncorhynchus mykiss)

“…An increase in cortisol levels related to clove oil anaesthesia has also been reported by Wagner et al (2002) in rainbow trout. On the other hand, Holloway et al (2004) found decrease of cortisol concentration in rainbow trout. In our experiments with rainbow trout, a significant increase (p < 0.05) in blood plasma glucose and ammonia immediately after the 10-min clove oil anaesthesia was observed.…”

Size-relative Effectiveness of Clove Oil as an Anaesthetic for Rainbow Trout (Oncorhynchus mykiss Walbaum, 1792) and Goldfish (Carassius auratus Linnaeus, 1758)

“…Clove oil has recently been studied as a potential anaesthetic for some ornamental fish (Kaiser et al 2006;Macova et al 2008) and several farmed cold and warm water fish species (Wagner et al 2003;Holloway 2004;Velisek et al 2005a,b;Hajek et al 2006, Gomulka et al 2008. However, results of several studies suggest that the physiology of fish can be affected by changes in the haematology and biochemistry of exposed fish.…”

“…Therefore it is important to assess the extent of physiological changes of fish exposed to an anaesthetic (Inoue et al 2005;Park et al 2008). Results of the numerous studies on clove oil revealed that effective concentrations for anaesthesia vary with fish body size and water temperature (Oikawa et al 1994;Hoskonen and Pirhonen 2006;Mylonas et al 2005;Zahl et al 2009) with the smaller fish being more responsive than the larger one (Holloway et al 2004;Velisek et al 2005a,b). Velisek et al (2005b) studied the effect of clove oil on juvenile and brood stock of rainbow trout (Oncorhynchus mykiss) but there are no data for larger sizes of this species, in particularly for the final growing stages (200-300 g) where size grading prior to harvesting may be required.…”