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The occurrence of pathogenic bacteria, Aeromonas hydrophila, in farm‐raised fish requires urgent attention. Continuous and indiscriminate use of antibiotics as growth promoters and disease control agents in aquaculture have been discouraged because of the risk of development of antibiotic‐resistant bacterial strains. There is steady interest in the use of botanicals, such as clove, Eugenia caryophyllata, buds extract (ECBE), as alternatives. Hence, the present study evaluated the effect of dietary ECBE supplementation on the growth performance, physiological, antioxidant, and immunity biomarkers of African catfish, Clarias gariepinus. Fish (11.7 ± 0.5 g) were fed diets containing 0.0 (control), 5.0, 10.0, or 15.0 g ECBE/kg diet up to apparent satiation twice daily for 12 weeks. After the feeding trial, fish from each treatment were challenged with A. hydrophila infection by intraperitoneal injection and kept under observation for 14 days to record any abnormal clinical signs and daily mortality. The results demonstrated that fish performance and feed intake were significantly enhanced with increasing ECBE levels, and its optimum level is 15 g/kg diet. Further, the dietary ECBE increased significantly the intestinal villi length/width and absorption area in a dose‐dependent manner. There are significant progressive increases in the values of red blood cells, hemoglobin, hematocrit, white blood cells, platelets, lymphocytes, and heterocytes, while monocytes, eosinophil, and basophils decreased significantly due to dietary ECBE in a dose‐dependent manner. Highest glucose, cholesterol, total protein, globulin, and albumin‐globulin ratios, aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), urea, and creatinine values were found in fish fed 15 g ECBE/kg diets, while lowest values were recorded in fish fed the control diet. Despite the high AST and ALT values, no visible lesions or damage were observed in the liver cells of fish fed ECBE‐enriched diets. In addition, the inclusion of ECBE in fish diets enhanced the antioxidant and immunity capacity. Fish mortality after the bacterial challenge was higher in fish fed the control diet (82.3%) than those fed ECBE‐enriched diets. The lowest fish mortality was observed in fish fed the 15 ECBE/kg diet (4.7%) [Correction added on 16 November 2018: this section has been revised for clarity.].

A study was conducted to assess the physico-chemical characteristics and fish distribution of wetland areas of Oyo State. The results revealed incidence of pollution as a result of agricultural pollution mainly due to use of agrochemicals. The water pH, Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) were below the World Health Organization (WHO) and FEPA permissible limit in all the locations with the exception of Ajinapa where 5.0, 226.8 mg/l and 372.6 mg/l were recorded for pH, BOD and COD respectively. The level of agrochemical usage varied significantly (p < 0.05) among the locations examined with Ajinapa (Orire LGA) having the highest rate (65.0%) while papa-Eleye (Oluyole L.G.A) had the lowest (15.0%). A total of 16988 individuals, 11 fish species belonging to 7 families were found in 11 locations with Oreochromis niloticus (30.6%) and Clarias gariepinus (20.8%) dominating the catches. From the result, it is clear that high level of pollution in Ajinapa (Orire LGA) location is traceable to the use of agrochemical and therefore there is a need to take appropriate measure to preserve the aquatic life.

An 84-day feeding trial was carried out to evaluate the effects of aqueous Psidium guajava leaf extract (PGE) on growth, intestinal morphology, physiology, immune response and susceptibility of Oreochromis niloticus to Aeromonas hydrophila. Diets containing 0% (P0), 0.25% (P1), 0.50% (P2), 0.75% (P3) and 1.00% (P4) PGE were fed to triplicate groups of fish (mean weight; 1.32 ± 0.04 g) for 84 days. After the 84-day feeding trial, test fish were injected with pathogenic A. hydrophila and then fed for 14 days. More feed were consumed in groups of fish fed PGE-treated diets and resulted in significantly higher weight gain and feed intake. Incidentally, there was an increase in the calculated area of absorption of fish fed PGE diets, as accounted for by marginally higher villi length and width. Antioxidant and immune response were improved with PGE inclusion in diets as total protein, superoxide dismutase, glutathione peroxidase and glutathione S-transferase significantly increased (p < 0.05) in fish fed PGE diets. Results of the challenge test with A. hydrophila revealed that the highest mortality (100%) was recorded in P0. This study revealed that inclusion of P. guajava extract in the diet of O. niloticus improved growth, nutrient utilization, immune system and survival of O. niloticus fingerlings. K E Y W O R D S Aeromonas hydrophila, growth, immune response, Oreochromis niloticus, Psidium guajavaChanges in weight were measured fortnightly (Orisasona, Falaye, Ajani, & Kareem, 2017) and values used in growth and nutrient utilization parameter determination. | Weight gainThis is as final weight of fish (W2) less initial weight (W1)Weight gain (g) = W2 − W1