Determination of Heavy Metal Concentration in Two Bony Fish (Catfish and Tilapia) from Orashi River in Rivers State, Nigeria

The research was intended to study the influence of human and industrial activities on the Orashi River and two bony fish (Clarias gariepinus and Tilapia nilotica). Three groups are observed to have impacted the environment – Oil/gas industries, tyre burning from abattoir, untreated human and animal waste from settlers and the abattoir. The study was carried out from September 2019 to August 2020. The mean concentrations of the parameters studied in some samples were close to or exceeded World Health Organization (WHO) and Federal Ministry of Environment (FMEnv) recommended limits for drinking water and seafood. The results from this study have provided information on the heavy metals profile on the fish of the river. The level of heavy metals in the muscle of Catfish and Tilapia showed a range of Cadmium in Catfish (1-3.9mg/kg and Tilapia (0.1-4.2mg/kg) with the highest level occurring in station 2 (3.47mg/kg for Catfish and 3.39mg/kg for Tilapia) which is high with regard to FAO 19835, FAO/WHO 10896, EEC 20054 permissible limit of 0.01mg/l and USEPA SQG (1mg/kg) level in seafood. The levels of essential heavy metals in fish muscle were Copper (Catfish-10.9-33mg/kg, Tilapia -17.3-40.6mg/kg), Iron (Catfish-1.0-2.5mg/kg, Tilapia -0.1-5.6mg/kg) were within the FAO 1983 permissible limit while Zinc (Catfish-22-213.2mg/kg) and Tilapia (30.1-196mg/kg) exceeds the limit in some stations. Catfish muscles recorded higher mean value (127.12mg/kg) for all heavy metals than tilapia (44.03mg/kg) and the sequence is Copper > Zinc > Iron > Cadmium. The concentration of heavy metals in Orashi River is in the sequence: Sediment > Catfish > Tilapia >Water. The Total Heavy metal concentration in muscle of Catfish (0.5-1.8mg/kg) and Tilapia (0.1-3.8mg/kg) were within permissible limit.