Stunted growth in pond-reared Litopenaeus vannamei was observed in different farms located in Tamil Nadu and Andhra Pradesh, India. No mortality was associated with stunted growth. PCR assay on these samples revealed the presence of Enterocytozoon hepatopenaei (EHP) in stunted shrimp. Tissue distribution of EHP in naturally and experimentally infected shrimp was studied by PCR and histology. Histological examination revealed the presence of EHP in hepatopancreas and gut, but not in other organs. The PCR assay revealed the presence of EHP in all the organs tested in both naturally and experimentally infected shrimp. Healthy shrimp were challenged with E. hepatopenaei by intramuscular injection and oral route, and no mortality was observed in both routes after 30 days post-challenge. Different developmental stages of the microsporidian parasite were observed in the hepatopancreatic epithelial cells. Biochemical parameters such as total protein, albumin, aspartate transaminase (AST), alanine transaminase (ALT) and alkaline phosphatase were measured in the haemolymph of naturally and experimentally EHP-infected shrimp. All biochemical parameters mentioned were found to be significantly higher in EHP-infected shrimp when compared to normal shrimp. This is the first report relating AST and ALT levels to EHP infection in naturally and experimentally infected shrimp.

Whiteleg shrimp, Litopenaeus vannamei, with clinical sign of muscle opaqueness with reddish colour at the distal abdominal segments were observed in farms located in West Bengal State, India. The mortality of shrimp in all disease outbreak ponds ranged from 20% to 50%, and mortality increased gradually. The RT-PCR assay of these samples using primer sets specific to infectious myonecrosis virus (IMNV) revealed its presence in the disease outbreak ponds. The IMNV infection was reproduced in healthy shrimp by intramuscular injection to satisfy River's postulates. The virus caused mortality in intramuscularly challenged shrimp, but failed to cause mortality by oral route. Tissue distribution of IMNV in infected shrimp by RT-PCR assay revealed the presence of this virus in haemolymph, gill, hepatopancreas and muscle. This study confirms that the disease outbreak which occurred in the shrimp farms located at Purba Medinipur District, West Bengal, India, was due to IMNV.

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Background: The present study was undertaken to analyse the monthly and seasonal finfish bycatch diversity of trawler fishery of Nagapattinam coast situated in the state of Tamil Nadu, South India from January 2017 to August 2019. Methods: Samples of finfish bycatch were collected fortnightly from the commercial shrimp trawlers operating in the coastal waters off Nagapattinam. The collected bycatch of finfish species was identified and month-wise and season-wise trawl finfish bycatch occurrence data collected were subjected to univariate and multivariate analysis using PRIMER Version 6.1.7. software. Result: In this study, the annual average total landing was estimated at 15,414.41 tonnes with an annual average fishing effort of 9327 boat days. Of this total landing, commercial catch constituted 70.75% (10,905.78 tonnes), whereas finfish bycatch formed 21.12% (3,256.14 tonnes) and rest by other groups. The peak fishing effort was observed in every March during the study period. A total of 210 finfish species belonging to 15 orders, 79 families and 153 genera were recorded, in which the order, Perciformes alone shared 53.81% of the total number of species. The monthly univariate analysis revealed that bycatch diversity was the highest in every September and the lowest in every June during the study period, while the season-wise analysis revealed the highest diversity during monsoon seasons. Likewise, the month-wise multivariate analysis performed through cluster analysis divulged the highest similarity between September’17 and September’18, while the season-wise analysis revealed the highest similarity between postmonsoon’17 and postmonsoon’18. Further, the K dominance plot divulged that the highest density of finfish species was in every September and in monsoon seasons during the study period.

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