Clove oil is an effective, local and natural anaesthetic. Many hatcheries and research studies use clove oil to immobilize fish for handling, sorting, tagging, artificial reproduction procedures and surgery and to suppress sensory systems during invasive procedures. Clove oil may be more appropriate for use in commercial aquaculture situations. Improper clove oil use can decrease fish viability, distort physiological data or result in mortalities. Because animals may be anaesthetized by unskilled labourers and released in natural water bodies, training in the proper use of clove oil may decrease variability in recovery and experimental results and increase fish survival. Here, we briefly describe many aspects of clove oil, including the legal uses of it, anaesthesia mechanism and what is currently known about the preparation and behavioural and pathologic effects of the anaesthetic. We outline methods and precautions for administration and changes in fish behaviour during progressively deeper anaesthesia and discuss the physiological effects of clove oil, its potential for compromising fish health and effectiveness of water quality parameters.

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Prebiotics, probiotics, and synbiotics have been successfully used in dietary supplements to achieve aquatic animal health and therefore increase the quality and sustainability of fish production. In the present study, four hundred and twenty common carps, Cyprinus carpio ( 25.37 ± 0.22   g ; mean ± SE ) were randomly attributed to seven treatments, fed with diets containing PrimaLac (probiotic), inulin (prebiotic), and Biomin Imbo (synbiotic), 1 and 2 g/kg for each supplement. After 60 days of feeding, an increase in final weight (FW), weight gain (WG), specific growth rate (SGR), and survival rate (SR) was recorded in the treatment groups compared to that of the control ( P < 0.05 ). The food conversion ratio (FCR) in the treatment groups significantly decreased ( P < 0.05 ). The treated groups showed significant improvements in serum immune parameters: lysozyme (LYZ), alternative complement (ACH50), total immunoglobulin (total Ig), and myeloperoxidase (MPO) ( P < 0.05 ). Feeding fish with supplemented diets significantly showed enhanced antioxidant status: catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx). Malondialdehyde (MDA) activity was significantly lower in fish fed dietary additives ( P < 0.05 ). Compared with the control group, enzyme parameters revealed that supplementation could significantly decrease alanine transaminase (ALT), alkaline phosphatase (ALP), and aspartate transaminase (AST) ( P < 0.05 ). The biochemical parameters including triglyceride (TRIG), cholesterol (CHO), glucose (GLU), and cortisol (CORT) decreased with dietary supplementation ( P < 0.05 ). Total protein (TP) increased in fish fed experimental diets ( P < 0.05 ). Fish fed pro, pre, and synbiotic exhibited significantly higher digestive enzymes (amylase, lipase, and protease) ( P < 0.05 ). Skin mucus parameters (total Ig, ACH50, LYZ, protease, and ALP) were significantly enhanced in groups fed dietary additives ( P < 0.05 ). Thus, the best recommended inclusion level of supplementation is 2 g/kg for inulin and 2 g/kg for PrimaLac and doses of 1 or 2 g/kg for Biomin Imbo. Dietary PrimaLac, inulin, and Biomin Imbo could be recommended as beneficial feed additives to enhance growth performance, innate immune and antioxidant systems, and promoted biochemical parameters and digestion of common carp; also, the effect of dietary synbiotic was superior to that of prebiotic and probiotic.