Bioaccumulation of heavy metals in some tissues of croaker fish from oil spilled rivers of Niger Delta region, Nigeria

Objective To investigate the level of heavy metals (Cu, Zn, Fe Mn Ni, Pb and Cd) in muscles, gills and liver tissue of Croaker fish from oil spilled rivers of Bonny and Finima, Niger Delta region, Nigeria. Methods Twenty four Croacker fishes (Genyonemus lineatus) weighing between 250 and 260 g and 24–26 cm length were collected from each sampling sites (Bonny and finima rivers). The frozen fishes were thawed and dried at 105 °C until they reach a constant weight. The dried samples were homogenized and digested with 10 ml tri-acid mixture (HNO