Microbial and heavy metal contamination of skipjack and yellowfin tuna from beaches in the Greater Accra Region, Ghana

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In Ghana and other parts of the world, consumption of fish and fishery products have raised serious health issues and is responsible for some of the reported deaths. Here, the microbiological contamination within the traditional smoking chain [freshly landed, after smoking and in the retail markets (smoked)] and heavy metal Hg, Pb and Cd levels of Skipjack and Yellowfin tuna from Accra Jamestown, Tema Canoe Basin and Prampram Lighthouse beaches in the Greater Accra Region, Ghana were studied. Aerobic Plate Count (APC) was done by the pour plate method and E. coli determined and enumerated by the Most Probable Number (MPN) method. Vibrio parahaemolyticus was determined by the spread plate method whilst heavy metal levels were analyzed using Atomic Absorption Spectrophotometer. APC values for fish were in the order 106, 104 and 102 in the retail market (smoked), at landing beaches (fresh) and at processing sites (smoked) for landing sites and species. There were significant differences (P < 0.05) for APC values at the various stages of production, the different landing beaches and the two species. Escherichia coli were present in freshly landed samples and also at the various retail markets for both species but not detected in fish sampled at the various smoking environment. Interestingly, Vibrio parahaemolyticus was not detected from all landing beaches and at all the stages of the production chain for both species. Fish handling practices clearly contributed to the high levels of microbiological loads after smoking. Heavy metal concentration showed no significant difference (P > 0.05) among different landing sites for both species. However for every metal, Yellowfin recorded significant higher levels (P < 0.05) compared to Skipjack. Together the study concluded that the mean concentrations of Hg, Pb and Cd in Tuna fish landed in the Greater Accra Region of Ghana were classified as low as per Ghana Standards Authority /European Commission/Food and Agricultural Organization requirements.
A thesis submitted to the Department of Theoretical and Applied Biology, Kwame Nkrumah University of Science and Technology in partial fulfillment of the requirements Master of Science degree in Environmental Science.