Comparative analysis of nutritional value of Oreochromis niloticus (Linnaeus), Nile tilapia, meat from three different ecosystems

Abstract

Determination of protein, lipid, and mineral content of fish meat is necessary to ensure that it meets requirements for food regulations and commercial specifications. The objective of the present study was to determine the chemical composition of Oreochromis niloticus (L.), Nile tilapia, under three different ecosystems: (1) high pollution and high density of Eichhornia crassipes, that is, water hyacinth (Lake Chivero), (2) medium pollution and medium density of water hyacinth (LakeManyame), and (3) low pollution and low density of water hyacinth (Lake Kariba). Drymatter, protein, lipids, and ash were evaluated by proximate analysis. Minerals were determined by atomic absorption spectrophotometry and pH was determined by a pH meter. Lake Kariba fish had the highest percentage of dry matter, protein, and ash. These qualities were correlated to low levels of pollutants and high oxygen content in the harvest waters. The phosphorus content of fish from Lake Chivero was very high, in tandem with phosphate levels in the harvest waters. In addition, water from Lake Chivero had an alkaline pH, high nitrate, and low oxygen content. The results suggest that effluent from sewage works and fertilizer industries caused pollution and proliferation of water hyacinth, contributing to pervasion of the chemical composition of fish.