Mapping the potential areas for enclosure fish culture in tropical reservoirs: geo-spatial solutions for sustainable aquaculture expansion

Planning aquaculture and fisheries activities in a reservoir requires knowledge of dynamics of water spread. We studied water spread dynamics of three reservoirs in the Godavari river basin, India using multi-temporal satellite imagery for the period 1990–2018 and developed a framework for mapping the spatial extent of water spread area (WSA) having potential for enclosure fish culture. The study showed that WSA of Nizamsagar reservoir in pre-monsoon season has declined from 108.11 to 99.34 km2 from phase I (1990–2006) to phase II (2007–2018), respectively and a similar trend was seen in Pocharam and Nallavagu reservoirs. For post monsoon seasons of the same time period, an increase in WSA was seen in Nizamsagar (133.75–144.14 km2) and Pocharam reservoirs (14.15-14.67 km2). Based on frequency of water presence during 2007–2018, WSA with potential for cage and pen culture was determined in Nizamsagar (31.04 km2) and Pocharam (2.87 km2) reservoirs. The study showed that both the reservoirs can accommodate maximum allowed number of cages (5000 and 500 cages respectively). We provide a decision matrix for location-specific selection of suitable culture methods and candidate species, which would aid in optimal utilization of the hitherto under-utilized reservoirs, especially in in situ data poor conditions. This study can be scaled up in the entire country with the help of academia/industry to prioritize reservoirs with potential for enclosure fish culture and plan appropriate interventions for reducing their yield gap.