Mass larval mortality in a giant freshwater prawn Macrobrachium rosenbergii hatchery: an attempt to detect microbes in the berried and larvae

Early mass mortality of Macrobrachium rosenbergii larvae is a big problem ofhatchery failure. Vibrio spp. and/or M. rosenbergii nodavirus (MrNV) have been reported to bethe major causes of mass mortality of M. rosenbergii larvae. An attempt was made to detect thereported bacterial and viral pathogens in the berried and larvae of M. rosenbergii. The berriedwere collected from the Kocha river, Pirojpur and brought to the hatchery. For detection ofbacterial pathogen, five berried were collected before the treatment with disinfectant and fiveberried were collected after the treatment and release of the hatchlings. Larvae samples werecollected from the larvae rearing tanks after five days and 15 days post-hatching. The sampleswere processed, inoculated in TCBS agar media and PCR was done using primers designed fromgroEL and 16S rRNAgenes for Vibrio sp. MrNV detection kit was used to detect MrNV. Wehave identified two bacterial species namely Morganella morganii and Citrobacter freundi in theberried samples. However, no Vibrio spp. nor MrNV was detected in either of the samples ofberried and larvae. However, mass mortality was observed in the hatchery resulting in a poor PLproduction. Therefore, other factors might be responsible for the mass mortality in the prawnhatchery that demands further in depth investigations.