Located in the southwest of the Province of Buenos Aires, it covers the districts of Villarino, Bahía Blanca and Coronel Rosales.  This reserve contains numerous islands such as Bermejo, Trinidad, Monte, Ariadna, Embudo, Conejo, Garzas and Zuraidas, as well as an important number of creeks and channels until reaching the open sea. It is a very rich environment in native flora and fauna and historical features. In its estuarine environments we find typical vegetation such as jume, glasswort and palo azul. Its most emblematic fauna is represented by the razor clam, whiting, dolphins, guanacos and the Olrog’s gull, in serious danger of extinction. The area preserves a stopover site for migratory birds, coastal ecosystems, and scrubland vegetation.

The main conservation challenges in the area are pollution from sewage and industrial effluents, and the expansion of the exotic Japanese oyster.