ASSESSMENT OF HEAVY METALS IN EDIBLE MUSCLE OF NILE TILAPIA (Oreochromis niloticus) AND CRUCIAN CARP (Carassius carassius) FROM LAKE ZIWAY

Abstract

Heavy metal is a general collection term applying to the group of metals and metalloids with an atomic density greater than 6g/cm3 and are mainly associated with pollution problems.The purpose of this study was to conduct analysis of heavy metal accumulation in the edible muscles of Nile Tilapia and Ccurican carp fish species which are among the most common types of fish consumed by the local people and found widespread in the lake.The water and fish samples were purposively collected from three sites in the Lake. The physicochemical properties of water samples such as Temperature, pH, electrical conductivity, total dissolved solids and suspended solids were measured and analysed. The analysis of heavy metals such as Cd, Pb, Ni, Cu, and Zn were conducted for water samples and from edible muscles of two fish species Nile tilapia and Curician carp. Data were subjected to statistical analysis. The result of physicochemical properties of the water samples from the study sites in the lake Ziway indicated no significance differences in temperature and pH among the three sites. However, significance differences were observed in other parameters like electrical conductivity (EC), total dissolved solids (TDS) and suspended solids (SS). Site 1(locally called bochessa) has demonstrated significantly the highest EC (1245.12±5.34 µS/cm), TDS (756.10±1.50mg/L) and SS (24.5±0.15 mg/L). The concentrations of heavy metals in water samples from Lake Ziway at site 1 (close to floriculture industry, locally called bochessa) presented significantly the highest amount of all the tested metals (Cd (2.71mg/L), Cu (4.88mg/L), Ni (8.10mg/L), Pb (6.06mg/L) and Zn (12.12mg/L). The accumulation of heavy metals in two fish species including Nile tilapia locally called ‘koroso’ and Curican carp locally named as ‘dabe ‘ demonstrated significant differences in the load of heavy metals between both species with Nile tilapia loaded significantly higher than Crucian carp in most of the metals assessed. The highest load of metal accumulations in fish muscles were observed at site 1 (near floriculture industry,locally called bochessa) in Nile tilapia with load of Zn(100.37), Cd (6.05), Ni(4.70), Pb (5.76) and Cu (47.54)mg/L.Similar study was conducted by Zenebe (2011) on lake Hawasa and Dessie et al (2019) on Lake Hayq. The comparison of heavy metal accumulation across lake sites in fish muscle samples indicated that the highest accumulations were obtained for Cu and Zn; small amounts of Cd, Ni & Pb. Lake Ziway needs contionous monitoring by concered bodies as well as all stake holders to use the lake in sustainable manner