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

Abstract

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