Mangrove forest and artisanal fishery in the southern part of the Gulf of California, Mexico

Abstract

Mangroves are among the most productive ecosystems worldwide due to the high organic flow within the same system and to adjacent ones. They also support a high diversity of terrestrial and marine fauna. Mangroves have been heavily exploited anthropogenically and destroyed for shrimp farming. An important amount of coastal commercial fisheries depend on mangroves during at least one stage of their life history and thus loss of mangrove habitat may alter their cycle. The San Ignacio–Navachiste–Macapule Lagoon area is strongly used by local fishermen for shrimp, blue crab, stripped mullet, snapper, and cockles. Landsat 5TM satellite of 1990, 1994, 1999, 2004, and 2009 images were used to process mangrove coverage with supervised classification. Fish landings were obtained from the regional and local fishery offices. We observed that the five fisheries together were strongly related to mangrove cover. A simple correlation between mangrove coverage and landings was carried out. Also, 119 fishermen were spatially referenced within the lagoon system and fishing gears were documented. A 90.67% precision and 0.86 kappa index was obtained, where errors were most frequent when classifying other vegetation as mangroves. Mangrove coverage did not change significantly between 1994 and 2009, ranging from11,886 to 11,929 ha. The five fisheries landings were 86,023 tons. Shrimp and blue crab catches were the most important species with ∼90% of the total catches. A positive and significant (p < 0.05) correlation was observed for all fisheries together and shrimp. Gillnet and cast net are the most important fishing gears used inside the lagoon, 31.09% and 24.37%, respectively. Strong correlations suggest the importance of mangroves to support coastal fisheries; however other anthropogenic pressures within the system such as fishing effort and eutrophication may play an important role in the resource availability.