Trace metal distribution in Tilapia zillii and Synodontis schall from the Siluko River, Edo State, Nigeria

Abstract

Metal pollution of aquatic ecosystems has raised concerns about their uptake by aquatic organisms and subsequent biomagnification along the aquatic food chain. This study determined trace metal distribution in Tilapia zillii and Synodontis schall from the Siluko River in Edo State, Nigeria. Fresh fish samples were harvested monthly from September 2021 to August 2022 with the assistance of artisanal fishermen. Trace metal contents in the gills, liver, and muscles were determined using atomic absorption spectrophotometer. The metal pollution index (MPI) was used to estimate the extent of metal bioaccumulation in the fishes. Results showed species variation in metal accumulation in various organs: T. zillii had a higher mean content of Cu, Zn, Mn and Fe in all the organs, while S. schall had a higher mean content of Ni, Cr, and Pb in all the organs. The MPI values ranged from 5.28 to 5.94 in the organs of T. zillii and S. schall. The order of MPI values in T. zillii was muscles > liver > gills; in S. schall, it was liver > gills > muscles. The results indicate trace metal contamination of fishes due to aquatic pollution. High MPI values is an indication of the degree of metal pollution of the Siluko River and the high susceptibility of these metals to bioaccumulation in the fishes. This predisposes the fishes to metal toxicity and portends health risk to fish consumers. The continuous monitoring of activities within the river watershed to mitigate heavy metal pollution is recommended.