Heavy metals bioaccumulations in Chrysichthys nigrodigitatus (Silver catfish) from River Oli, Kainji Lake National Park, Nigeria

Heavy metals have become a public health problem worldwide in recent years due to their potential toxic effect and ability to bio-accumulate in aquatic ecosystems. Therefore, this study examined heavy metals bioaccumulation in Chrysichthys nigrodigitatus from River Oli, Kainji Lake National Park. The concentrations of Pb, Cd, Fe, Cr, Zn and Cu in fish body part samples (mg/kg) were determined with AAnalyst 200 model of Atomic Absorption Spectrophotometer (AAS).
The results showed that there were significant variations in heavy metals concentration across fish muscles, vertebral bone and gills. The level of Fe accumulation is significantly varied in all fish body parts where muscles accumulated most (218.33±7.50) while gills had least (185.33±19.50). Concentration of Pb was significantly higher in muscles (6.55±0.51) and lower in gills and vertebral bones (5.71±0.07 and 0.66±0.10, respectively). Concentration of Cd showed no significant difference in all samples and its bioaccumulation in fish parts was relatively low. In muscles, the bioaccumulation profile was Fe>Cu>Zn>Pb>Cr>Cd. While in gills, the profile was Fe>Zn>Cu>Pb>Cr>Cd and it was Fe>Zn>Cu>Cr>Pb >Cd in vertebral bones.
Results showed that fish accumulated essential metals in their muscles with higher levels than non-essential metals. However, considering the importance of this species to food security and ecological stability of the study area, the level of Pb and Fe accumulation in various fish parts are of great concern because both elements exceed the WHO minimum permissible limits of 2 mg/kg and 100 mg/kg for Pb and Fe respectively in food and food products.