The dataset contains records of otter (Lutra lutra, Mammalia) collected in plots along lower river Tua sub-basin and included in theEcological monitoring Program of the Foz Tua Hydroelectric Dam, promoted by EDP – Energias de Portugal, S.A. Data were collected in November 2010 and March 2011, during field visits to 12 sampling plots with favourable habitats for otter located in the lower river Tua and some tributaries. The occurrence of the target taxa was documented through 22 observations of scats identified as belonging to the target species.

The dataset contains records of otter (Lutra lutra, Mammalia) collected in the Rivers Tua and Douro sub-basins and included in the Complementary Studies (2009-10) of the Environmental Impact Assessment of the Foz Tua Hydroelectric Dam, promoted by EDP – Energias de Portugal, S.A. Data were collected in February 2010 during field visits to 41 sampling points with favorable habitats in 16 10x10 km UTM squares in the river Tua sub-basin and in five sampling points in the river Douro, close to the the Tua mouth. The presence of individuals was recorded by direct observation of signs (scats).