Coastal Marine MPA
Bahía San Blas
Wildlife Refuge and Multiple Use Nature Reserve

Cover Photo © Guillermo Harris


The Bahía San Blas Multiple Use Nature Reserve is located on the maritime coast of the Patagones district, in the extreme south of the province of Buenos Aires. San Blas and Anegada Bays are composed of a group of islands, banks connected by an extensive network of shallow water channels, with an extensive intertidal zone. The environment is completed with brackish water marshes, small islands and islets and other estuarine environments, with sandy beaches, other stony beaches and some coastal dunes. The vegetation corresponds to halophilic steppes (adapted to environments with little water availability). There are large crayfish beds in the area, which are feeding grounds for migratory birds. Migratory coastal birds, seabirds, marine mammals, rays, and sharks are found in the reserve. The red shorebird and Nearctic migratory species that visit the area during their migration are threatened. The area is noted for the existence of large colonies of the crabeater gull, an endemic and endangered species of the southwestern Atlantic coast. Together with the Bahía Blanca estuary ecosystem, they concentrate approximately 90% of its breeding population. The reserve’s coasts and waters are used by numerous species of marine mammals, especially the franciscana, an endemic species at great risk of extinction. The area is also home to the most important sea lion colony in the province of Buenos Aires. Its coastal waters are used by a large number of endangered species of rays and sharks.

Geographic Location


Buenos Aires


-40.28° Latitude S

-62.13° Longitude W

Size and Limits

Total Area:


Marine Area (Multiple Use Nature Reserve):


Superficie Continental (Wildlife Reserve):


Surface area estimated based on the calculation of the area of the polygon represented on the map (ArcGIS PRO) with an Albers Conic Equivalent projection to preserve surface area calculations.

OPDS de Bs. As. reports 3910 km2 (OPDS Read More)
APN reports 1219.13 km2 for the Wildlife Refuge and 3967.48 km2 for the RNUM Read More)

Legal Aspects



Year of Creation


Creation Legislation

Provincial Law 12788 (repeals Law 10492)

Eco-regions represented


Argentine Province Ecoregion of the Buenos Aires – Uruguayan Platform


Espinal Ecoregion

Conservation Objectives

Located in the Patagones district, San Blas Bay and Anegada Bay, it consists of a set of islands, banks and shallow waters, with an extensive intertidal zone. The environment is completed with brackish water marshlands, small islands and islets and other estuarial environments, with sandy and stony beaches, and some coastal dunes. The vegetation corresponds to halophilic steppes, that is, adapted to brackish environments and xerophilic scrub, and environments with little water availability. There are large mud flats, that in addition to being feeding sites for migratory birds, provide shelter for the reproduction of a great variety of marine birds.

Colonies and stopover sites

The following table presents the colonies or stopover sites of some emblematic species of birds and marine mammals present within the MPA boundaries.


Management effectiveness and evaluation year

34 % – METT Evaluation (2014)

Year of Management Plan approval


Sources of information consulted: Management Plan (2008).
Bird and marine mammal colonies: See bibliography