Selection of Sustainable Locations for Fish Farms in the Amazon Region of Northern Brazil Using Geophysical and Sedimentological Data

In recent years, aquaculture operations in northeastern Pará, in northern Brazil, have expanded at a much faster rate than the national average, to the extent that the region is now an important national fish farming nucleus. While this region has enormous potential for aquaculture given its vast water resources, it faces a range of problems, including the need to select adequate sites to guarantee the sustainability and success of fish farming operations, as a source of food for the local population. The present study was based on the integration of direct (sedimentological analysis) and indirect methods [ground-penetrating radar (GPR) and seismic surveys] to evaluate the characteristics of a proposed fish farming site in the Amazonian town of Braganca, in northern Brazil. The GPR data revealed that the subsoil has horizontal to subhorizontal layers, with the presence of a water table at a depth of 6–7 m. The subsoil has a sandy substrate mixed with clay, as confirmed by the shallow-refraction seismic data. The classification of the soil also confirmed this diagnosis, with a predominance of sand (mean = 64.43%), and clay (mean = 22.72%) and silt (mean = 12.85%) in smaller proportions. These percentages are well below the recommended values (25% clay and 45% clay + silt) needed to ensure a minimum loss of water from the excavated substrate through infiltration. Overall, the analyses confirmed that the site surveyed here was not adequate for the installation of fish farming ponds. The study integrated two geophysical methods (GPR and seismic) and sedimentology to assess the site of a proposed fish farm, and provided a highly effective diagnosis of the characteristics of the proposed fish farm, which can be extended to other aquaculture operations in the study region.