Análisis de la cobertura del Bosque de Manglar y su correlación con la pesca ribereña entre 1993 y 2009 en el sistema lagunar San Ignacio-Navachiste-Macapule, Sinaloa, México

Abstract

Mangroves are one of the most productive ecosystems worldwide due to the immense organic flow within the same system and to adjacent ones. They also support a great amount of diversity of both terrestrial and marine fauna. Mangroves have been heavily exploited antropogenically for their use as wood for construction and cooking and they are also destroyed for shrimp farming. An important amount of coastal commercial fisheries depend on mangroves during the important stages of their life cycle and thus loss in mangroves may alter them. Lagoon complex, San Ignacio-Navachiste-Macapule has a big mangrove extent which is strongly used by fishermen and therefore mangrove cover and landings of shrimp, blue crab, mullet, snapper and cockles’ relationship was evaluated. Landsat 5TM, path/row: 33:42, satellite imagery (1990, 1994, 1999, 2004 and 2009) was processed and coverage change was analyzed with supervised classification. Landings were obtained from Guasave and Mazatlan local fishery offices from 1993 to 2009. 5 fisheries strongly related with mangroves were selected and total annual landings and CPUE were determined for the five fisheries together and for each one separately. Correlation between mangrove cover and landings was carried out. Also, interviews were done to fishermen engaged on a fishing activity and their spatial position was obtained with GPS (n=119). Data from fishing gears was spatially processed with geographic information system software. A 90.67% precision and 0.86 kappa index was obtained where errors were most frequent classifying other vegetation as mangroves. Mangrove coverage did not change significantly between 11886 and 11929 from 1994 to 2009. 86023 tons of the five fisheries were reported being shrimp and blue crab catches the most important with approximately 90% of the total catches. A positive ad significant (p<0.05) correlation was observed for both the fisheries together and shrimp. Mullet, blue crab and cockles had a high correlation (r2>0.07) even though no significance was detected. Although small cover change in mangroves was detected catches and CPUE of shrimp since 2005 and from 2002 for mullet have considerably reduced. Gillnets and cast net are the most important fishing gears inside the lagoon (31.09% y 24.37%). Statistical differences between fishing gears and proximity to mangroves were obtained. Strong correlations suggest the importance of mangroves to support coastal fisheries, however other anthropogenic pressures within the system such as fishing effort and eutrophization may play an important role in the resource availability.