Distribution patterns of the golden mussel Limnoperna fortunei (Mollusca – Bivalvia) under different salinities on Patos-Mirim, drainage basin, RS – Brazil

Abstract

The distribution of Limnoperna fortunei (Dunker 1857) in the southern region of Lagoa dos Patos and Lagoa Mirim were analysed (2001-2006), and the species distribution were described. The predominant low salinities on the Lagoa dos Patos region between 2001-2003 resulted in massive colonization of L. fortunei in the northern portion of the estuarine region, and an isolated occurrence in the southern, close to the lagoon mouth. In contrast, between 2004 and 2006, a salinity increase occurred, due to severe periods of drought in the RS state. This increase in salinity caused the mortality of the populations in the estuarine region below 31º 20' and in the northern sector of the São Gonçalo channel, which binds the Lagoa dos Patos to Lagoa Mirim. The registers of low salinity occurred during a period of formation of the phenomenon "El Niño", while that of high salinity, in 2004, in the southern portion of the lagoon has been caused by a period of low precipitation, leading to a decrease in the lagoon water level, fact that has been related to the phenomenon "La Niña". The identification of the sceneries that regulate the distribution and persistence of opportunistic species like as L. fortunei in the Patos Lagoon, and its associated conditions supplies subsidies for future accompaniment of this species distribution, assisting in action of prevention of its harmful effect to the estuarine/lagunar region.