Bacterial contamination and heavy metal residues in frozen shellfish retailed within Lagos metropolis, Nigeria

Abstract

Shellfish has become a worldwide delicacy amongst seafood lovers due to its essential nutrients which are beneficial to human health. An investigative study was carried out on eight different shellfish– White Shrimp (Penaeus occidentalis), Tiger Shrimp (Penaeus monodon), Pink Shrimp (Farfantepenaeus notialis), Guinean Mantis Shrimp (Squilla aculeata calmani), Royal Spiny Lobster (Pallinurius regius), Lagoon Crab (Callinectes amnicola), Smoothswim Crab (Portunus validus) and Periwinkle (Tympanotonus fuscatus) obtained from Better Life market- exploring their bacterial quality and heavy metal accumulation. The highest Total Bacterial Count (2.71±0.03×10⁸ CFU/g) was observed in P. occidentalis while the lowest count (1.00±0.04×10⁸ cfu/g) was observed in T. fuscatus. The Total Faecal Count of the shellfishes reduced under 44⁰C temperatures except in P. occidentalis which increased from 1.40±0.05×10³ to 1.70±0.01×10³ CFU/g. Although, all identified bacteria (Bacillus spp, Escherichia coli, Lactobacillus spp, Pseudomonas aeruginosa and Klebsiella spp ) were found in C. amnicola and T. fuscatus but the most contaminated shellfish was Penaeus occidentalis, with 38.5% E. coli, followed by F. notialis having 37.3% P. aeruginosa. The mean heavy metals concentration occurred in the following decreasing order: Iron> Zinc> Copper> Chromium> Manganese while Cadmium, Lead, Nickel and Arsenic were not detected in most of the samples. The study revealed that frozen shellfish are preserved under unhygienic environment most times and the fact that some levels of toxic metals were found in the samples is a cause for constant monitoring.

Keywords: Heavy metal, Bacterial, Shellfish, Frozen, Makoko, Nigeria