GLOBAL JOURNAL OF FISHERIES SCIENCE
Integrity Research Journals
ISSN: 2782-750X
Model: Open Access/Peer Reviewed
DOI: 10.31248/GJFS
Start Year: 2018
Email: gjfs@integrityresjournals.org
Bacterial load and pathogenic isolates in commercially important freshwater fish from River Niger, Onitsha, Nigeria: Food safety implications
https://doi.org/10.31248/GJFS2026.105 | Article Number: 9106327F1 | Vol.8 (3) - July 2026
Received Date: 30 April 2026 | Accepted Date: 01 June 2026 | Published Date: 30 July 2026
Authors: Ikeogu, C. F.* , Okpala-Ezennia, K. P. and Chukwudi, O. G.
Keywords: Artisanal fisheries, Aquatic microbiome, freshwater fish, riverine ecosystem, total viable count.
Maintaining the microbiological safety of fish is essential for safeguarding public health, particularly in freshwater systems increasingly impacted by anthropogenic activities. This study evaluated the bacterial load and diversity of three commercially important freshwater fish species (Citharinus citharus, Marcusenius kainjii, and Synodontis membranaceus) obtained from two major landing sites (Niger Street and Ose Marine) along the River Niger at Onitsha, Nigeria, with emphasis on food safety implications. Fish samples were collected weekly in May 2024 and analysed for total viable bacterial counts (TVC) and bacterial isolates using standard culture and biochemical methods. Total viable count values ranged from 6.52 to 6.59 log10 CFU g-1, falling within generally accepted limits of 7.0 log10 CFUg-1 by the International Commission on Microbiological Specifications for Foods for fresh fish but indicating moderate microbial loads. Gill tissues from Niger Street landing site (6.53 log10 CFU g-1) and Ose Marine landing site (6.59 log10 CFUg-1) showed higher bacterial counts than skin (6.52 log10 CFU g-1 and 6.59 log10 CFUg-1 respectively), thereby reflecting greater environmental exposure. A diverse bacterial community was identified, dominated by Vibrio spp. and Shigella spp., alongside Escherichia coli, Staphylococcus spp., Streptococcus spp., Clostridium spp., and Klebsiella spp. Similar bacterial genera were detected in water samples, demonstrating a strong environmental linkage. Although bacterial loads were within acceptable limits, the presence of potentially pathogenic genera highlights a critical limitation of relying solely on total viable counts as indicators of food safety. The findings indicate that microbial contamination in the study area is driven by a combination of environmental pollution, faecal inputs, and post-harvest handling practices. This study emphasises the need for integrated monitoring approaches utilising quantitative and qualitative microbial assessments, alongside improved wastewater management and hygienic handling practices, to enhance fish food safety and protect public health.
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