Available online at: www.mbai.org.in doi: 10.6024/jmbai.2017.59.2.2014-05 Evaluation of suitable sites for mud crab farming in Ratnagiri District of Maharashtra, India K. Vinod, P. K. Asokan, P. U. Zacharia, P. Kaladharan, V. V. Singh, A. P. Dinesh Babu, N. K. Sanil, A. Anasukoya, D. D. Sawant, Girish Gopinath1, Bhaskar Paul2 and N. Vasudevan2 ICAR-Central Marine Fisheries Research Institute, Ernakulam North P.O., Kochi – 682 018, Kerala, India 1Centre for Water Resources Development and Management, Kunnamangalam, Kozhikode – 673 571, Kerala, India 2Mangrove Cell, Mumbai, Department of Forests, Government of Maharashtra Correspondence e-mail: [email protected] Received: 31 Oct 2017 Accepted: 18 Dec 2017 Published: 5 Jan 2018 Original Article Abstract aquaculture. The sediment pH ranged from 6.2 to 8.32. The organic The State of Maharashtra has vast stretches of estuaries, creeks and carbon levels in sediment ranged from 0.27 to 2.94% indicating medium mangrove swamps, which offers great potential for aquaculture, to high productive nature of sediment. Samples of mud crab collected from particularly for mud crab farming. In view of the natural resources and the study areas were processed for screening for WSSV infection. All market potential for mud crab, the Department of Forests, Government of samples gave Negative results in primary as well as nested PCRs, Maharashtra plans to promote mud crab farming through a novel indicating the absence of WSSV in the wild mud crab population. approach, which aims at providing livelihood support to the local Integrating the analysis result along with supporting spatial data with the communities utilizing the mangrove wetlands; thereby the local aid of GIS and Remote Sensing techniques, a total of 10.063 ha have been communities also shoulder the responsibility of conservation of mangroves. evaluated as suitable areas for mud crab farming along the brackishwater In this backdrop, a study was conducted to identify the suitable sites for stretches of Anjarle (1.91 ha), Aade (2.069 ha), Kelshi (1.77 ha), Velas sustainable mud crab culture, in GIS environment, based on various (0.538 ha) and Ansure (3.776 ha). physical and environmental criteria including topography, soil types, land- use systems, vegetation, water quality, water availability, salinity, risks of Keywords: GIS, Maharashtra, mud crab farming, potential areas, flooding, infrastructure, seed resources and availability, market and Ratnagiri 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 mucronataand Acanthus ilicifolius. The pH of water was near-neutral to alkaline, whereas dissolved Introduction 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 The brackishwater mangrove swamps is one of the most generally varies with the tide. The ammonia levels which ranged from 0 biologically productive habitats of the coastal and marine (Aade and Ansure) to 0.5 ppm (Kelshi), falls within the safe levels for ecosystem, and act as a buffer zone between land and the J. Mar. Biol. Ass. India, 59 (2), July-December 2017 Evaluation of sites for mud crab farming in Ratnagiri District sea (Hegazy, 2003; Wolf, 2012; Jusoff, 2013; Lee et al., 2014, The State of Maharashtra has vast stretches of estuaries, creeks Vijaya Kumari Nunna, 2016). The mangroves act as a shield and mangrove swamps which would have great potential for against the vagaries of storms, cyclones and other natural farming of finfishes and shellfishes. The mud crab, Scylla serrata disasters and play a significant role as protectors of shorelines is one of the good candidate species, which has great demand (Fritz and Blount, 2007; Latief and Hadi, 2007; Spalding et al., in local markets as well as in the export markets. 2014). They help to prevent erosion by stabilizing sediments with their tangled root systems (Prasetya, 2007; Lang’at et al., The local communities play a vital role in the protection of 2009; Spalding et al., 2014). They are also capable of filtering mangroves as they share a symbiotic relationship with this the pollutants and trapping sediments originating from land ecosystem. Sustainable mangrove conservation by local (Tam and Wong, 1995; Spalding et al., 2014). The mangrove communities can happen when they start deriving tangible habitats are home to a variety of life forms like invertebrates, benefits from protecting the mangrove ecosystem (Vasudevan and fish, amphibians, reptiles, birds and even mammals. They are Goenka, 2017). Thus, the Department of Forests, Government of also ecologically significant as they serve as breeding and Maharashtra aims to promote mud crab farming in the mangrove nursery grounds for many of the commercially important fin ecosystems as a part of conservation of mangroves. This novel and shell fishes (Alistar and Duke, 1987; Sasekumar et al., approach aims at providing livelihood support to the local 1992; Laegdsgaard and Johnson, 1995; Acosta and Butler IV, communities utilizing the mangrove wetlands, and thereby the 1997; Abu El-Regal and Ibrahim, 2014). The mangrove trees local communities also shoulder the responsibility of conservation are harvested for water-resistant wood for building houses, of mangroves. In this backdrop, a study was conducted to evaluate boats, furniture etc. Some mangrove trees are good source of the mud crab farming potential in some of the brackishwater charcoal and some of them serve as source of dyes which are areas of Ratnagiri District of Maharashtra, in GIS environment, extracted from the barks. Some mangroves are also known for based on various physical and environmental criteria including their medicinal properties. The mangrove habitat is a rich source topography, soil types, land-use systems, vegetation, water quality, of commercially important fishes thereby providing income to water availability, salinity, risks of flooding, infrastructure, seed scores of coastal communities. Therefore loss of mangroves resources and availability, market and support services. would have direct economic repercussions on the coastal people. Material and methods There has been a continuous decline in mangrove forests caused by The study was conducted in brackishwater stretches of Ansure, various factors: for example, conversion to agriculture, reclamation Anjarle, Aade, Kelshi and Velas in the Ratnagiri District of for aquaculture, urban development and tourism (Upadhyay et Maharashtra (Fig. 1). al., 2002; Sahu et al., 2013), and according to the Government of India (1987) report, India lost 40 per cent of its mangrove area in the last century. The reduction in mangrove area will increase the threats due to cyclones, erosion and flooding, besides affecting the coastal water quality and reduction in biodiversity. The decline in mangrove vegetation will also lead to release of large quantities of stored carbon, exacerbating the process of global warming and climate change. Considering the enormous ecosystem services provided by mangroves, there is an urgent need to conserve this valuable ecosystem. There are wide range of methods for conservation such as developing sanctuaries, community sacred groves and mangrove plantation programmes (Selvam et al., 2003; Khan et al., 2008; Bhatt and Vivekanandan, 2013; Upadhyay et al., 2015; Vasudevan and Goenka, 2017). However, any conservation programme would be successful if only all the stakeholders including the local communities are involved in the conservation efforts. The mangrove cover in Maharashtra had remained constant at 186 sq. km. since 2005 till 2013; but showed a remarkable increase to 222 sq. km by 2015 and 304 sq. km by 2017 (FSI, 2017). Maharashtra has been proactive in conservation of mangroves and it has notified 15,087.6 hectares of mangroves across the state as reserved forest, and thus became the first state in the country to do so. Fig. 1. Map showing the study locations in the Ratnagiri District of Maharashtra © Marine Biological Association of India 37 K. Vinod et al. Collection and analysis of water and sediment Preparation of GIS maps and evaluation of potential mud crab farming sites Field surveys were conducted in the study areas, along with the beneficiaries identified for mud crab farming by the Forest Geo-referenced Google map having Universal Transverse of Department. During the field surveys, the mangrove species Mercator (UTM) Zone 43 N projection systems were used as were identified and information on pollution, water retention base map for the study. The GPS locations of sampling sites etc. were gathered from the local people. The depth of the were overlaid on the base map and boundaries were digitized study stations were measured by suspending a weight from using analysis tool in ArcGIS 10.3 software. Buffer analyses the boat. The geo-location of each of the sampling sites were were performed using geo-processing Tool of Arc GIS 10.3 recorded using GPS (GARMIN Montana 680). The surface and demarcated the suitable sites for sustainable mud crab water samples were collected in clean plastic bottles and culture. Areas for each zone were calculated using statistical were analysed for various physicochemical parameters like analysis of Arc GIS. temperature, salinity,