Along the Jaguaripe, Paraguaçu and Subae Rivers ten, nine and ten sampling stations, respectively (Fig. 1), were established in or- der to cover the entire salinity gradient of each (see Barros et al., 2012). Data collection occurred between March and November 2011, during low spring tides. Margins with small human settle- ment and sedimentary rocks outcrops were avoided and, whenever