The concentrations of the constituent minerals calcium, iron, potassium, magnesium, phosphorus, zinc, copper, iodine, selenium and nickel were determined in the muscle tissue of the following seven species of fish collected in the lower stretch of the Itapecuru River, northeastern Maranhão, Brazil: Plagioscion squamosissimus, Geophagus surinamensis, Curimata sp., Schizodon dissimilis, Ageneiosus ucayalensis, Hypostomus plecostomus and Prochilodus lacustris. Samples of muscle were digested in a nitric-perchloric solution and then analyzed using an inductively coupled plasma (ICP) atomic emission spectrometer (Model 720-ES, VARIAN brand) and specific calibration curves for each element. Analyses were performed in triplicate. The analyzed individuals were small in size. The shortest total length of 6.7 cm was observed in G. surinamensis, and the longest total length of 38.7 cm was observed in P. lacustris. With regard to total weight, the minimum and maximum values were 11.0 g and 465.3 g for the species P. squamosissimus and H. plecostomus, respectively. The concentrations of all minerals can be considered low and are present in concentrations below the maximum limits established by the Brazilian legislation for human ingestion of fish. A comparison of the seven investigated species of fish revealed no statistically significant differences between the concentrations of minerals, suggesting that the size and dietary habit differences did not exert an influence on absorption.
Keywords:Fish, Soft tissue, Minerals, Spectrophotometry, Itapecuru River, Brazil.