ISSN 2360-7971
Abstract
The objective of this study is to investigate the effect of the toxicity of formalin on Oreochromis niloticus in Wudil, Kano State, Nigeria. An experimental design was adopted for this study which involves two sets of experiments: determining the acute toxicity of formalin and the therapeutic effect of formalin. The method for the acute toxicity test as recommended by Yadav and Singh (2009) was also employed. The research was conducted at the fish laboratory of the Biological Science Department, Nigeria Police Academy, Wudil, Kano. The Nigerian Police Academy is located in Wudil, Kano State, Nigeria. A total number of 36 tilapia juveniles (Oreochromis niloticus) were collected alive from River Wudil. Formalin was obtained as 40% formaldehyde. The following concentrations were administered to each of them: 0.5, 0.1, and 1.5 mg/l and a control with 0.00 mg/l. Each concentration had 4 treatments. 3 juveniles of the specimen were randomly selected and stocked in each of the 12 plastic bowls, and the experiment was set randomly. A static bioassay was then used to determine the toxicity test of formalin for Oreochromis niloticus juveniles. Another set of fish infested with Cichlidogyrus spp. in aquaculture habitual conditions was exposed to different concentrations of formalin, and then observation was done to find the concentration range that effectively treats the disease or parasite while minimising the harm to the fish. Changes in appearance and mortality were also recorded. All data obtained were subjected to one-way analysis of variance (ANOVA) using the Statistical Package for Social Sciences (SPSS), version 23 for Windows. Differences in means were separated using Duncan’s new multiple range test (DMRT). The level of significance was determined at the P = 0.05 level of probability. The significant difference was established at a 5% probability level (P < 0.05), while the results generated were expressed as mean ± standard deviation (SD). The results showed that at the concentration of 0.5 mg/l, the mean values of the fish mortality were 0.00, 0.00, 0.00, 0.33, 0.33 and 0.67 mg/l. While at concentration 1.0, mean values of fish mortality were 0.00, 0.33, 0.33, 0.00, 0.67 and 0.33, and at a concentration of 1.5 mg/l, mean values are 0.00, 0.67, 0.33, 1.00, 1.00 and 1.33. At 0.00 concentration, there was no fish mortality at all. The study showed that formalin has a therapeutic effect on fish infested with Cichlidogyn spp. It was therefore concluded that the use of formalin in a lesser concentration based on this study is safe for tilapia (Oreochromis niloticus). Also, if the period of exposure of the fish does not exceed 6 hours, it is not going to be toxic to Oreochromis niloticus. Moreover, there is effectiveness in using formalin to reduce the infestation of fish by parasites. The study recommended that indiscriminate use of formalin in water impoundments should be avoided, especially when the concentration is high to preserve fish diversity, among others.
Keywords: Acute Toxicity, Formalin, Oreochromis Niloticus, Juvenile, Aquaculture.