Status of trace metals in smoked Clarias gariepinus cultured in earthen pond in Lagos state, Nigeria

Catfish consumption has risen over the last 2 decades with its popularity more pronounced in a cosmopolitan, commercial and industrial region like Lagos state. However, there is a need to measure the level of anthropogenic induced impacts on the safety level of fish production within this environment for human consumption. This research determined the level of trace metals bioaccumulation within the three senatorial districts of Lagos state. A total of nine (9) fish farms (three from each senatorial district) operating earthen ponds were randomly selected. Water samples from the farms were also collected and analyzed for heavy metals. Fish samples were smoked before analysis. The trace metals such as chromium, cobalt, iron, lead, aluminum and copper and manganese was analyzed using Atomic Absorption Spectrophotometer. The result of the trace metals were 0.07 – 0.13 mg/kg (lead), 0.01 – 0.02 mg/kg (chromium), 6.75 – 7.77 mg/kg (iron), 3.05 – 3.89 mg/kg (manganese), 0.05 – 0.07 mg/kg (copper), 0.00 – 0.01 mg/kg (cobalt) and 0.00 – 0.01 mg/kg (Aluminum). Statistically, there is no significant difference (P>0.05) among the various locations except for aluminum. The trace metal levels were below the tolerable or allowable level for fish food as recommended by Food and Agricultural Organization or World Health Organization, Median international standard, European Union, United State Environmental Protection Agency and Water Pollution Control Legislation for fish food. The detection of lead above standard in the water suggests the need for frequent monitoring of the water quality and fish food to prevent possible toxicity that could arise from the consumption of the fish food from the study area.