Many mangrove areas have been cleared for intensive exotic shrimp culture (Penaeus vannamei), but this economic activity has decreased in recent years. Shrimp ponds are constructed enclosing a mangrove area with dams (aprox. 2 m height) constructed with mangrove wood and mud; trees are chopped and retired, and chemical products added to increase soil pH to levels compatible with shrimp development. Surveying the river we found an area cleared in 2003 but abandoned before ponds were completely implemented ( Fig. 1B). This experimental area encompasses a mosaic of preserved mangrove, shrimp ponds and secondary riparian forest. Partially constructed dams did not impaired hydrologic features of area, which receives brackish water from high intertidal fringe and experiences semidiurnal tides. However, during the tree clearing the soil was physically altered and populations of crabs greatly affected. The area was originally dominated by R. mangle, with far lower abundance of L. racemosa. In spite of high numbers of R. mangle and L. racemosa propagules being brought by tides from surrounding mangroves, only very sparse (