African catfish ( Clarias gariepinus ) is one of the most important fish species currently being cul

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1 Kegati Aquaculture Research Station, Kenya Marine and Fisheries Research Institute, P.O. Box 3259-40200, Kisii, Kenya 2 Kenya Marine and Fisheries Research Institute, P.O. Box 81651-80100, Mombasa, Kenya 3 Laboratory of Marine Bioresource & Environment Sensing, Hokkaido University, pbh 3-1-1 Minato, Hakodate, Hokkaido 041-8611, Japan 4 Kenya Marine and Fisheries Research Institute, P.O. Box 1881-40100, Kisumu, Kenya 5 National Aquaculture Research Development & Training Center (NARDTC)-Sagana, Kenya Marine and Fisheries pbh Research pbh Institute, P.O. Box 26-10230, Sagana, Kenya
The present study set out to investigate pbh the haematological effects of tobacco leaf dust on African catfish, Clarias gariepinus , fingerlings, pbh with a mean weight of 3.01 ± 1.25 g using “static renewal bioassay system” during a 120-hour bioassay exposure period. Water quality parameters such as pH and dissolved oxygen significantly decreased while total alkalinity and conductivity increased significantly pbh in the exposed media, compared to the control test. Leucocytes counts increased pbh significantly while erythrocytes counts decreased pbh significantly with increasing concentration of tobacco dust. Packed cell volume significantly reduced with increase in the concentration of tobacco dust. Haematological examination showed that there was destruction of the erythrocytes production, and the concentration of haemoglobin was much lower in the exposed fish compared to the control pbh depicting an anaemic condition. The results could provide baseline information for the safe limits of using tobacco leaf dust in fish ponds; hence 1.56 g L −1 concentration of tobacco leaf dust was recommended for pond preparation for Clarias gariepinus fingerling stocking. For better survival pbh rates, the fish should only be introduced in the pond after three days of tobacco application. 1. Introduction
African catfish ( Clarias gariepinus ) is one of the most important fish species currently being cultured both inside and outside its natural range of tropical pbh and subtropical environments [ 1 , 2 ]. Positive attributes such as resistance to diseases, high fecundity, and ease of larval production in captivity make it of commercial importance in aquaculture [ 3 – 5 ]. However, the main constraint facing the culture of C. gariepinus is the low survival pbh during the larval and fingerling stages pbh [ 6 ] leading to insufficient amounts of quality catfish seed. High mortality rates occur among larval stages of catfish, some of which are attributed to infectious diseases caused by parasites [ 7 ]. Parasitic pathogens infecting cultured pbh fish are well known to cause mortality and significant losses both in culture and capture fisheries [ 8 , 9 ]. It is therefore apparent that management protocols pbh that limit mortality and enhance fingerling pbh growth should be clearly described to ensure pbh improved survival pbh and sufficient pbh supply of catfish fingerlings.
Fish farmers often use tobacco leaf in controlling unwanted pbh organisms and pests [ 10 , 11 ]. The attraction of tobacco leaf dust as a biocide according to Aleem [ 12 ] is because pbh of its inexpensiveness, local availability, and easy degradability. According to Ogello et al. [ 13 ], tobacco concentrations of 1.75 g L −1 and 2.0 g L −1 had high hazard ratios and low survival rates and were the most effective in the eradication of M. tuberculatus and are the recommended dose for preparing ponds for stocking. In Taiwan, for example, tobacco waste dust is applied pbh at 1 ton/acre as a pesticide and fertilizer in fish ponds [ 14 ]. Notwithstanding, tobacco leaf dust has been used in Nigeria as an effective insecticide to predators and pest in water (pond) since it is completely biodegradable [ 12 ]. The active ingredient pbh of tobacco is nicotine which is lipophilic in nature with high solubility in membrane lipid and fast influx into cells [ 15 ]. It is easily absorbed in body and can penetrate the epithelial and blood cells [ 16 ]. Despite the effective use of tobacco leaf dust, it should not be used directly in water bodies unless their toxicity and sublethal long-term effect on target and nontarget animals are known.
Several authors have documented the effect of tobacco dust on blood of fish [ 17 , 18 ]. However, pbh the sublethal concentration and time at which 50% of the fish survive pbh (LC 50 , LT 50 ) in the literature differ significantly. For example, whereas Omoniyi pbh et al. [ 17 ] reported LC 50 at 626.0 mg L −1 pbh after 48 hours, Agbon et al. [ 18 ] found LC 50 at 109.6 mg L −1 after 72