A study on the proximate composition and mineral distribution in tissues of Nile tilapia (Oreochromis niloticus) from Gilgel Gibe Reservoir, south-west Ethiopia

Abstract

Fish is the most important food valued for its nutritional qualities. It is rich in protein, vitamins, polyunsaturated fatty acids and minerals. Nile tilapia (Oreochromis niloticus) is the most abundant and commercially important fish species in Ethiopia. The present study was aimed at analyzing tissue proximate composition, mineral distributions in tissues and analysis the fatty acid profile and amino acid of Nile tilapia. Deneba and Bore sites were selected based on the accessibility of the Reservoir. From each site, ten fish samples were collected. Then blood samples and targeted tissues (muscle, gill, skin, stomach and liver) were collected from all fish samples. Finally, all the samples were processed for further analysis of proximate composition and minerals following the procedure in Association of Official Analytical Chemists. Data were analyzed both qualitatively and quantitatively. Variations were observed between the tissues both in terms of proximate composition and mineral distribution. Accordingly, lowest (69.39 ± 1.99%) and highest (81.44 ± 0.102%) moisture content were recorded in skin and muscle, lowest (7.49 ± 0.36%) and highest (21.89 ± 121%) crude protein were recorded in stomach and skin, lowest (0.71 ± 0.003%) and highest (7.92 ± 0.24%) crude fat were recorded in muscle and gill, lowest (1.12 ± 0.023%) and highest (7.24 ± 0.09%) ash content were recorded in muscle and stomach tissues respectively. High levels of saturated fatty acid were obtained from the blood analyzed and followed by monounsaturated fatty acid and then polyunsaturated fatty acid. Amino Acid profile indicated the fish was rich source essential amino acid. The minerals were accumulated specifically within each tissue. Relatively stomach accumulated higher concentration of minerals and followed by liver and gill. While skin and muscle store less amounts minerals compared to the other tissues. The value recorded for some toxic minerals were above the recommended uptake limit that needs concerns. Gill, liver and stomach could be the preferable tissues that used as a bioindicators of aquatic pollution.