Selectivity of gillnets targeting Hemiodus unimaculatus in the lower Tocantins River, Amazon, Brazil

Abstract

The authors set out to determine the selectivity curves of the nets that capture the jatuarana, Hemiodus unimaculatus (Bloch, 1794). The study site corresponds to the area located upstream of the dam of the Tucuruí­­ Hydroelectric Power Plant. The collections were made quarterly in 2001, 2003, 2005, 2006 and 2007 and semiannually in the years of 2002 and 2004 in five sites in the reservoir and in two upstream, using a battery of gill nets 50 m long and 3 m height, with meshes of 40, 60 and 80 mm between opposing nodes. The selectivity was determined through the construction of the selection curves, indicating that the 60 mm mesh is the most suitable for fishing, considering the capture of 50% of adult individuals.