Benefits of stocking white spot syndrome virus infection free shrimp (Penaeus monodon) post larvae in extensive ghers of Bangladesh

Abstract Shrimp farming is an important income generating activity for hundreds of thousands of small scale farmers operating extensive ghers in Bangladesh. White spot syndrome virus (WSSV) has caused major shrimp production losses globally including Bangladesh. This study investigated the benefits of stocking WSSV infection free (WSSVF) Penaeus monodon post larvae (PL) to extensive gher holders of southwest Bangladesh and considered different parameters of the farming system. The longitudinal observational study included 636 gher holders comprising two distinct PL user types; 312 gher holders had stocked polymerase chain reaction (PCR) tested WSSVF and 324 non-tested (NT) PL. Data on explanatory and outcome variables were collected fortnightly during April–October 2015. The major findings were: (i) gher holders who stocked WSSVF PL had significantly higher survival, less disease, higher shrimp production and increased profitability compared to NT PL users, (ii) WSSVF PL stocking had an influence in strengthening the resilience, overall management and economic performance of the extensive gher holders. The study showed that WSSVF PL users had significantly small ghers, higher levels of better management practices (BMP) compliance such as nursery rearing of PL, double netting at inlet, periodic sampling, net fencing and bird netting, significantly higher application rates and usage amount of inputs (lime, inorganic fertilizer, feed) compared to NT PL users. It also found that gher size, water depth, stocking density, stocking frequency, cropping patterns affected levels of shrimp survival, production and disease incidence of the overall population. The results suggested that improving the availability of WSSVF PL through a PCR testing service, production of specific pathogen free PL and limit/stop the sale of WSSV infected PLs could significantly increase shrimp production of extensive gher holders.