Relationship of Biometric Size-Weight, Nutritive Value, and Metal Concentrations in Clarias lazera (Cuvier and Valenciennes) Reared in Treated Wastewater

The objective of the present study was to investigate the nutritive value and heavy metals accumulation in the flesh of Clarias lazera (Cuvier and Valenciennes) reared in the discharge canal of Soba wastewater treatment station, south Khartoum, Sudan. A total of 57 fish were collected from the canal and 52 from the White Nile which served as the control. The proximate composition of fish and concentrations of eight hazardous heavy metals i.e. chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), lead (Pb), robidium (Rb), strontium (Sr), and mercury (Hg) in the flesh of C. lazera were measured. The results which were statistically analyzed revealed insignificant differences in moisture, ash, fat contents, energy value, and fat: protein ratio (P 0.05) between the two studied sites. A significant difference (P 0.05) was evident in the protein content of fishes from both locations. Heavy metals accumulation in Clarias tissues differ from one element to another depending on each element characteristics and local environmental conditions e.g. Sr was higher in the White Nile fishes than in treated wastewater fishes (P 0.05). Accumulation of Pb and Hg was comparable in wastewater and White Nile (P 0.05). Fe, Cu, Zn and Rb concentrations were significantly higher in treated wastewater fishes than natural water fishes (P 0.05). Cr was also higher in treated wastewater fishes (P 0.05). Nevertheless, the concentrations of most considered elements were lower than levels recommended by various international agencies.