Laguna Sontecomapan

Sontecomapan Lagoon fills an alluvial plain between the Los Tuxtlas and Santa Marta ranges in Catemaco municipality, about 10 km northwest of Lake Catemaco. Its protected name is Manglares y Humedales de la Laguna de Sontecomapan: the Ramsar Convention listed it on 2 February 2004 as site no. 1342, covering 8,921 hectares, and it lies within the Los Tuxtlas Biosphere Reserve.

The open water is roughly 3 km wide and 4 km long, with a ragged outline. Rivers from both ranges and the region's heavy rain feed it fresh water, while the sea comes in through a channel about 4 km long that bends sharply east before reaching the Gulf of Mexico. Sand carried by the current has partly closed the mouth, so only launches and other small boats get through.

The Ramsar description singles out an important mangrove forest for the western Gulf coast, together with seasonally flooded low forest, reedbeds and coastal dunes. Migrating birds following the coast between North America and Central and South America stop here, and the site shelters species that are threatened in Mexico, among them the mantled howler monkey, the neotropical otter, the Muscovy duck and the uniform crake. The mangroves are spawning and nursery grounds for sea fish, and the freshwater marshes hold fish found only in this region, such as Priapella olmecae and Atherinella ammophila.

Fishing is the lagoon's main livelihood, with cattle and small farms on its shores. Clearing of the forest is still the biggest threat, though it has slowed since protection. Around 1960 the area was almost empty; today boat trips leave from the dock in Sontecomapan village on the southwest shore and run out to La Barra, the fishing hamlet on the sandbar between lagoon and sea.