Mud Crab Reovirus (MCRV) has been found to be the reason for the mass mortality of wild crab (Scylla serrate) in Andhra Pradesh.
Joint research by M.S. Swaminathan Research Foundation (MSSRF) and Centre for Advanced Study in Marine Biology (Annamalai University, Tamil Nadu) has confirmed the presence of MCRV in the samples collected from Nagayalanka fields and open markets in Krishna district. Since 2019, the mortalities were noticed by the MSSRF in the areas of Machilipatnam and Nagayalanka in Krishna district.
MCRV, also known as Sleeping Disease, has taken a toll on wild crab in every farming method; crab fattening and crab polyculture in which shrimp and wild crab are cultured in the same pond and exclusive mud crab ponds.
In 2014, the Central Institute of Brackishwater Aquaculture (CIBA-Chennai) introduced the crab fattening technology in Andhra Pradesh.
Nature of virus
“MCRV is responsible for the mass mortality of wild crabs. The viral pathogen belongs to the family of ‘Reoviridae’. It mainly affects the connective tissue of hepatopancreas, gills, and intestine,” SSRF Director (Coastal Systems Research) Dr. Ramasubramanian and Dr. Ayyagari Gopalakrishnan (Annamalai University) said. In 2007, the MCRV paralysed the wild crab species cultivation in China.
A group of wild crab farmers recently appealed to the CIBA-Chennai Scientists to help decide the future course of action in the wake of rising mortality of the wild crab in the Diviseema region of Krishna district.
“We are still to get any word from the CIBA scientists on the measures to tackle the mass mortality and management of the existing ponds,” Nagayalanka-based brackishwater farmers told The Hindu .
According to the A.P. State Fisheries Department, the total area under wild crab cultivation in Andhra Pradesh is around 25,000 acres including 4,500 acres in Krishna district by 2019. The wild crab cultivation is in the districts of Nellore, Prakasam, Guntur, Krishna, and Godavari districts. Beginning from 2019, at least 60% of cultivation has been affected due to mass mortality in the State.
Wild crab is directly exported to the South-east Asia region from coastal Andhra Pradesh. However, it has a large market in Europe, according to MSSRF.