Multi-criteria based geospatial assessment to utilize brackishwater resources to enhance fish production

Abstract

The growing demand for protein food and stagnating capture fisheries production is forcing researchers to explore alternative water resources and technologies to increase fish production. The aquaculture site suitability assessment in water bodies would ensure that the selected waterbody will provide a conducive growing environment for fishes without affecting the prevailing environmental ecosystem and the associated activities. Our study assessed the suitability of sites for cage aquaculture in the tropical estuarine ecosystem (Muttukadu-near Chennai, India) using the analytical hierarchy process based multi-criteria decision support spatial analysis. Consequently, 17 functions influencing cage culture were identified and categorized into water quality (pH, temperature, salinity, biological oxygen demand, dissolved oxygen, total ammonia nitrogen, nitrate, nitrite, phosphate, and Chlorophyll), environmental (water depth, water current flow, turbidity and distance to mouth bar) and infrastructure (distance to the seed source, transport and market). The measured variables were interpolated through inverse distance weighted spatial analysis and reclassified to the most suitable and unsuitable extent. The analytical hierarchical process (AHP) based pairwise comparison matrix was used to derive the weightage for each criterion, based on its relative importance. The uncertainty analysis using Monte Carlo simulation was carried out to address the probabilistic variations in AHP judgments. The weighted linear approach has been used to integrate all parameters to generate the output map, that indicates most suitable (5.9%) and suitable (8.1%) area available for cage and pen culture practices. Though the water quality parameters were almost suitable for aquaculture, the depth of water was the major influencing parameter in the estuary, which varied from 0.12 to 3.08 m during the lowest tide. Proper management of the mouth of the river sand bar, ensuring smooth water exchange between sea and estuary, would aid in maintaining the water suitability throughout the year. The present study is the first report indicating as to how geospatial planning in water bodies could help support local communities and the government to make use of the hitherto unusable brackishwater resources as a supportive livelihood option in developing countries.