Evaluation of suitable sites for mud crab farming in Ratnagiri District of Maharashtra, India

Abstract

The State of Maharashtra has vast stretches of estuaries, creeks and mangrove swamps, which offers great potential for aquaculture, particularly for mud crab farming. In view of the natural resources and market potential for mud crab, the Department of Forests, Government of Maharashtra plans to promote mud crab farming through a novel approach, which aims at providing livelihood support to the local communities utilizing the mangrove wetlands; thereby the local communities also shoulder the responsibility of conservation of mangroves. In this backdrop, a study was conducted to identify the suitable sites for sustainable mud crab culture, in GIS environment, based on various physical and environmental criteria including topography, soil types, landuse systems, vegetation, water quality, water availability, salinity, risks of flooding, infrastructure, seed resources and availability, market and support services. The brackishwater stretches of Anjarle, Kelshi, Aade, Velas and Ansure in the Ratnagiri district of Maharashtra were studied, and all study stations had patchy to thick mangrove vegetation. The major mangrove species encountered were: Avicennia marina, Avicennia officinalis, Sonneratia caseolaris, Rhizophora mucronata and Acanthus ilicifolius. The pH of water was near-neutral to alkaline, whereas dissolved oxygen levels were found to be within the ideal range. The salinity of the tidal creeks ranged from 7.24 ppt (Velas) to 35.9 ppt (Ansure) which generally varies with the tide. The ammonia levels which ranged from 0 (Aade and Ansure) to 0.5 ppm (Kelshi), falls within the safe levels for Available online at: www.mbai.org.in doi: 10.6024/jmbai.2017.59.2.2014-05 aquaculture. The sediment pH ranged from 6.2 to 8.32. The organic carbon levels in sediment ranged from 0.27 to 2.94% indicating medium to high productive nature of sediment. Samples of mud crab collected from the study areas were processed for screening for WSSV infection. All samples gave Negative results in primary as well as nested PCRs, indicating the absence of WSSV in the wild mud crab population. Integrating the analysis result along with supporting spatial data with the aid of GIS and Remote Sensing techniques, a total of 10.063 ha have been evaluated as suitable areas for mud crab farming along the brackishwater stretches of Anjarle (1.91 ha), Aade (2.069 ha), Kelshi (1.77 ha), Velas (0.538 ha) and Ansure (3.776 ha).