A study of the spatial distribution and abundance of fiddler crabs was carried out in Guaratuba Bay, Parana State, southern Brazil. Fiddler crabs were collected from 10 biotopes located along a salinity gradient from zero to 32 inside Guaratuba Bay (between 48°30'W-25°50'S and 48°45'W-25°54'S). Seven species were found, among which, Uca mordax (Smith, 1870) occurred only in biotopes inundated by low salinity water, from zero to 16. Remaining species tolerated wide range of salinity oscillation, but Uca maracoani (Latreille, 1802-1803) and Uca leptodactyla Rathbun, 1898 predominated in saltier waters, from 14 to 32, while U. burgersi Holthuis, 1967, Uca rapax (Smith, 1870), Uca thayeri Rathbun, 1900, and Uca uruguayensis Nobili, 1901 were collected in more than three biotopes and showed to be euryhaline: they tolerated salinities from 4 to 32. However, other soil characteristics such as pebble/sand/silt/clay balance, organic matter content and presence of seagrass also influenced the spatial distribution of these crabs. U. leptodactyla occurred with maximum density of 240 ind.m-2, a highest recorded value.
Density; granulometry; organic matter; salinity gradient
