Its presence is detected in waters very next to the coast, between the south of the Brazil and the south of the province of the Chubut. It resists and one adapts to changes of salinity and temperatures very pronounced well, and although its reproductive behavior is not known exactly, esteem that approaches towards brackish waters in estuaries and lagoons. Like his inner water brothers, it has a body esbelto, fusiform laterally and tablet, that concludes in pedúnculo of great volume relatively high. It has grudges of medium size and relatively small head, where the snout occupies the fourth part. The mouth, protráctil and with small teeth in both jaws, does not reach the height of the eyes that are of moderate size. It has two dorsal fins, the first hardly perceivable one because it is of few radii and it is squashed against the body. The second, enough one more back, has a greater base and is higher. The fin of great volume is truncated, the base of the anal is approximately equal to the length of the pectoral ones and the ventrals are born where the pectoral ones finish. All their fins are very transparent. Rare time is a unit greater to 35 cm , that normally are females; the males are of very inferior statures.