Abstract
Since the first record of white spot disease (WSD) in 1996, PCR tested, white spot virus (WSV) free post larvae of Penaeus monodon (Fabricius 1798) are stocked in grow-out farms as the major bio-security measure. However, significantly high mortality in young shrimp and total rejection of harvest have been recorded in North Western Province, Sri Lanka due to WSD and/or vibriosis. Present study was planned to identify critical better management practices (CBMPs) and critical bio-security measures (CBSMs) that should be strictly adopted to prevent the entry and spread of WSV and pathogenic Vibrio in grow-out farms of P. monodon. A questionnaire survey, carried out at randomly selected 100 grow-out farms located in the North Western Province, revealed that there was a relationship between the occurrence of WSD and /or vibriosis and levels of practicing better management practices (BMPs) and/or bio-security measures (BSMs). Proper pre-stocking pond preparation, adoption of zero water exchange, monitoring and controlling water quality parameters including pathogenic Vibrio in culture water and use of a suitable bioaugmenter and a probiotic were identified as the CBMPs while proper disinfection of culture water, stocking of WSV and MBV free post larvae and prevention of WSV contamination through other routes over the rearing period were the identified CBSMs. Entry and spread of WSV and pathogenic Vibrio in P. monodon grow-out farms in the North Western Province, Sri Lanka could be prevented by strict adoption of CBMPs and CBSMs identified during the present study.
Highlights
The shrimp farming generates export earnings with tremendous employment opportunities, and has a great potential for further development in Asia (Subasinghe 2015; Thitamadee et al 2016)
There was no farm in the high category in relation to adopting better water exchange system and no farm was adopting the use of beneficial bacteria as a probiotic (BMP-8)
All the grow-out farms had adopted the stocking of white spot virus (WSV) negative post larvae (BSM-2), which is mandated by the National Aquaculture Development Authority, Sri Lanka
Summary
The shrimp farming generates export earnings with tremendous employment opportunities, and has a great potential for further development in Asia (Subasinghe 2015; Thitamadee et al 2016). Epizootics of both infectious and non-infectious etiology have continuously plagued both production systems (hatchery system and grow-out system) of the shrimp farming industry (Walker and Mohan 2009). The most important pathogenic bacteria affects shrimp in both hatchery and grow-out systems and causes chronic or mass mortalities and shell deformities reducing marketability of shrimp (Lavilla-Pitogo et al.1990). Common pathogenic Vibrio species both in P. monodon hatchery and grow-out systems in the North Western Province, Sri Lanka have been isolated and identified (Kumara 2016; Kumara and Hettiarachchi 2016, 2017)
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