The Mangrove-Estuarine Complex Of Marismas Nacionales (Pacific coast of Mexico) As a Habitat For Fisheries

Marismas Nacionales is a marine flood plain system located in the pacific coast of Mexico considered the most extensive mangrove region of the American Pacific. This region is an important region for fisheries since prehispanic times with high biodiversity and an important wintering region for migratory birds from Canada and USA. Significant hydrological changes occurred in this region at the beginnings of the 70´s when an artificial channel was opened connecting the sea to the main water body. During the time the channel was build its width increased from 40 m in 1972 to 300 m in 1985 and to 1.5 Km in 1995 due to the sand barrier erosion as consequences of strong ebbs currents. This and other hydrological changes in the site and in the upper basin caused the dead of more than ten thousands hectares of mangroves. On the other hand, the opening of the artificial channel improved the shrimp and fish fisheries in the region and the adjacent marine waters. The fishermen communities surrounding the system and the catch of shrimp and fish increased more than 5 times after 1978. Several publications make reference of the importance of mangrove as a key habitat for sustainable fisheries, but environmental conditions in mangroves can be extremely difficult for the survival of fishes, crustaceans and mollusk (i.e. oxygen depletion) and for several authors its role is more related for supporting the fisheries in the surrounding habitats as the tidal channels, the intertidal sand banks, seasonal flood plains (“marismas”), coastal lagoons and the adjacent marine areas than “in situ” mangroves. We propose the hypothesis that mangroves need to be combined with freshwater inputs, tidal channels and coastal lagoons with tidal influence and seasonal floodplains in order for them to be highly productive areas for fish and fisheries. The relation between mangroves and tidal influence is directly related to fisheries production. Basin and dwarf mangroves play other ecological functions more important than supporting fisheries.