The present study was carried out in the Taquari Valley, central region of Rio Grande do Sul State, Southern Brazil. Between December 2001 and December 2002 a study about the predation of Cichlidae by Lontra longicaudis (Olfers, 1818) was performed through scale analysis found in otter scats. Predation was indentified about Gimnogeophagus labiatus (Hensel, 1870) and Crenicichla punctata Hensel, 1870, and the occurence of these fish species in the diet were higher than the relative availability in the environment. A positive correlation between fish and scale sizes was found, allowing to build a regression curve to estimate the size of predated fish, based on scales found in otter scats. In this study ciclids most frequently predated varied in lenght from 100 and 150 mm and in weight from 22 to 37,6 g.
Cichlidae; diet; otter; preferential predation; prey size estimation
