I. TONGO

Antibiotics have been used in fish farms for the treatment of bacterial infections. The indiscriminate use of these antibiotics has however led to the issue of antibiotic residue in food animals, which has emerged globally as a public health risk. Lack of information on antibiotic residue in catfish (C. gariepinus) in developing countries such as Nigeria is however a major problem. This study was carried out to evaluate the concentration of tetracycline residues in catfish (C. gariepinus) from selected ponds in Edo Central, Edo State, Nigeria. Adult Catfish (C. gariepinus) samples were obtained from three ponds in Edo Central and analysed for tetracycline residue using the QuEChERS sample method for residue analysis. Questionnaires were also administered to catfish farmers to evaluate their antibiotic use and knowledge of antibiotic administration. The tetracycline residue present in catfish from the sampled ponds were above the maximum residue limits (MRL). Pond 1 had the highest mean tetracycline residue (1.87 ± 0.03 mg/kg) while Pond 2 had the lowest mean tetracycline residue of the sampled ponds (1.84 ± 0.05 mg/kg).

Pesticide contamination in aquatic organisms poses a growing concern for both food safety and environmental health. This study evaluated the effect of boiling on the residual levels of organochlorine and organophosphate pesticides in the African freshwater prawn (Macrobrachium vollenhovenii) obtained from markets in Benin City, Edo State, Nigeria. Prawn samples were collected from Uselu and Oba markets in August 2025. Pesticide residues were extracted and analysed using Gas Chromatography–Mass Spectrometry (GC–MS). Results showed that twenty (20) organochlorine and fourteen (14) organophosphate pesticide residues were detected in both raw and boiled prawn samples. The total concentration of organochlorines decreased from 28.42 ppb in raw samples to 23.845 ppb after boiling, indicating a slight reduction following heat treatment. Conversely, organophosphate pesticide levels increased from 8.595ppb in raw prawns to11.405ppb in boiled samples. Among organochlorines, α-HCH, β-HCH, PP‘-DDT were eliminated after boiling while Gamma-Chlordane, Alpha chlordane, PP‘-DDD, Methoxy For organophosphates, Chlorpyrifos (2.405 ppb) and Phosalone (1.58 ppb) showed notably higher levels of post-boiling, whereas Isazophos and Pyrazophos were completely degraded. For both pesticide groups, the estimated daily intake (EDI) for local consumers, based on an average prawn consumption rate of 0.33 kg/day and a 60 kg adult body weight for both the raw and boiled samples, were below the acceptable daily intake (ADI), indicating minimal potential health risks. Similarly, the hazard quotient (HQ) and hazard index (HI) values for both pesticide groups were less than one (<1) for both the raw and boiled samples, implying low non￾carcinogenic and carcinogenic risk to consumers. When compared with the FAO/WHO Codex and EU maximum residue limit (0.01 mg/kg for seafood), the total concentrations of organochlorine pesticides (0.028 mg/kg) exceeded the acceptable limit, indicating potential xiii xiv contamination risks. These findings suggest that while boiling can reduce certain persistent organochlorine residues, it may also increase the apparent concentration of some organophosphate pesticides. Continuous monitoring and further investigation into the effects of cooking methods on pesticide dynamics are recommended to safeguard consumer health.

The presence of pesticide residues in aquatic organisms has become a growing public health concern due to the extensive use of agrochemicals and their potential to contaminate water bodies and aquatic food resources. This study focused on the determination of pesticide residues in the African freshwater prawn, Macrobrachium vollenhovenii, obtained from Oba Market. The aim was to assess the levels of pesticide contamination and evaluate potential risks associated with human consumption. Fresh prawn samples were randomly collected from different vendors in the market and transported to the laboratory for analysis. The samples were processed, extracted, and analyzed for selected pesticide residues using standard analytical techniques such as Gas Chromatography (GC) following appropriate extraction and clean-up procedures. The results revealed the presence of various pesticide residues, including organochlorine, organophosphate, and pyrethroid compounds, in varying concentrations within the prawn tissues. Some detected residues were found to be within permissible limits established by international regulatory agencies, while others approached or slightly exceeded recommended thresholds. The occurrence of these residues indicates possible environmental contamination of aquatic habitats resulting from agricultural runoff, improper pesticide disposal, and other anthropogenic activities. The study highlights the need for continuous monitoring of pesticide residues in aquatic food products sold in local markets to ensure food safety and protect public health. It also emphasizes the importance of implementing stricter regulations and promoting environmentally sustainable agricultural practices to minimize pesticide pollution in aquatic ecosystems. The findings provide useful baseline information for policymakers, environmental agencies, and public health authorities regarding pesticide contamination in seafood consumed in Benin City.

The issue of water pollution by nanometals in aquatic bodies has become of increasing concern since the rapid development of metal nanoparticles (NPs). Despite the usage of these nanoparticles, they also have negative impacts on fish. This study sought to assess the acute combined effect of Aluminium and Zinc Oxide nanoparticles on Superoxide Dismutase and Malondialdehyde activities of x catfish (Clarias garienpinus) embryo/lavae The Organization for Economic Development (OECD) Fish Embryo Acute Toxicity Test (OECD 236) was employed. Superoxide Dismutase and Malondialdehyde activities were assessed using standard procedures. Fertilized embryos were exposed to different concentrations of Aluminium and Zinc Oxide nanoparticles (0, 0.5, 1, 10 μg/L) for 48 h. The results showed a significant (p < 0.05) dose-dependent decrease in MDA and SOD activities in fish embryo/larvae, indicating that nanoparticles-induced a significant reduction in MDA and SOD activities. The findings suggest that Aluminium Oxide and Zinc Oxide nanoparticles could potentially impact the MDA and SOD activities of fish which could invariably affect the survival of aquatic life, especially catfish'