Mangrove shrimp farm mapping and productivity on the Brazilian Amazon coast: Environmental and economic reasons for coastal conservation

Abstract

The present study evaluates the role of marine aquaculture in the conversion of mangrove forests into shrimp (Litopenaeus vannamei, Boone, 1931) farms using remote sensing and geographic information system techniques and analyzes the productivity of the installed farms in the mangroves and adjacent coastal plateau. The extension of the shrimp ponds was quantified using satellite image analysis, and the water quality of the shrimp farms was analyzed based on measurements of dissolved oxygen concentration, temperature, pH, and salinity. The productivity of the farms was measured using biometric data. The data were analyzed using ANOVA with Tukey's post-test. The results indicated that shrimp farms cover an area of ∼0.8 km2 (approximately 0.4% of Brazilian ponds), of which 29.4% are located within areas of mangroves, and 70.6% are located in the coastal plateau. Saltwater aquaculture contributed to the conversion of 0.53 km2 of the mangroves into rearing ponds, which represents only 0.007% of the total area of the Amazonian mangroves. The installations in the mangrove presented significantly higher pH, temperature, transparency, and salinity compared with the ponds installed in the coastal plateau, although coastal plateau ponds had higher dissolved oxygen concentrations. Based on these differences, the mean sizes of the shrimp raised in the mangrove and coastal plateau ponds were 5.7 g and 4.3 g, respectively. However, the estimated value of one hectare of mangrove is much higher than its potential value in the production of shrimp. The considerable value of the ecosystem services provided by the mangroves indicates that the production of shrimp in the coastal plateau is relatively less damaging in ecological and economic terms. Thus, we can consider that the production of shrimp in the coastal plateau instead of in mangrove areas is less damaging to the long-term conservation of mangrove forests, which follows the management best practices established by international organizations. The coastal zone is considered a common resource that belongs to all citizens in Iberoamerican countries, and it is defined as a zone of non-building. Therefore, we conclude that mangroves are more valuable intact than converted into aquaculture ponds. Hence, aquaculture activities in the Amazon coastal plain are not sustainable from environmental and socioeconomic perspectives.