PHYSICO-CHEMICAL ANALYSIS OF WATER, SEDIMEN~"AND SOME. FISH SPECIES FROM ASA-DAM IN" KW-AnA S~:ATE, NIGERIA

Abstract

Fish samples tTilapia, Bagrus, Mormyrus, Chrysichthys and Parachanna) were collected from Asa Dam in Kwara State, Nigeria. Water and sediment were also sampled from the dam. Proximate analysis of the fish samples were carried out on the muscles. The moisture content values for the respective fish muscles were 80.70 ± 2.14%,76.71 ± 2.22%,78.39 ± l.04%, 69.34 ± 1.43% and 79.86 ± 2.25%, whereas the crude protein values were 15.89 ± l.100/0, 16.00 ± 0.51%, 16.09 ± l.310/0, 17.62 ± 2.12% and 17.58 ± l.41% respectively. The results showed that fish muscles must be consumed immediately due to high moisture content. The crude fat contents of the fish muscles were found to range between 1.55 ± 0.56% and 11.53 ± 0.66%, which suggests that consumption of oily fish and their products would give adequate energy. Low values were however obtained for ash content, which ranged between 0.28 ± 0.23% and 1.26 ± 0.16%. The concentrations of sodium, potassium, calcium, magnesium, zinc, lead, copper, manganese, iron and cobalt were determined in water, sediment and fish muscles. The fish muscles were found to contain high concentration of potassium, sodium and magnesium (62.0 - 106.40mg/kg, 48.63 - 82.73mg/kg and 11.32 - 141.60mg/kg, respectively), while lead, copper, cadmium and cobalt were not detected. The scales of tilapia and parachanna fish samples with a relatively high concentration of all the metals except copper might be useful in feed formulation. The physico-chemical properties of water sample from the dam were also determined. pH, total alkalinity and total hardness values for water were 6.9 ± 0.06, 52.50 ± 3.54 and 46.00 ± 0.20 mg/l, respectively. The chloride, sulphate, phosphate and nitrate values were 92.01 ± 0.02, 11.50 ± 0.21, 14.02 ± 0.33 and 10.80 ± 0.28 mg/l, respectively. These values fall within WHO standards and the water might be safe for both human and animal consumption as well as industrial purposes. The analysis of the sediment revealed that the biogenic metals - Ca, Mg and K (metals that support life) were the most abundant. Ca occurred in sample sediment at a concentration of 79.50 mg/kg, Mg 50.45 mg/kg, and K 74.90 mg/kg. All the metals tested for were present ill a reasonable quantity except for Cd and Co. Cd occurred as 0.04mg/kg and Co gave 0.07 mg/kg, therefore, occurrence of Cd and Co in little quantities in the sediment sample is an indication that the soil of Asa-Darn had not been polluted by the heavy metals. Calculations of simple correlation coefficients, r showed that the concentrations of metals in the three matrices showed a relatively high rvalues. Aqueous metal concentration showed best correlations among each other. The r-values were significantly different for both water and sediment, water and fish muscles, and sediment and fish muscles as confirmed by the output of the analysis of variance conducted using the Duncan multiple rangc test at P<0.05.