Enumeration of Vibrio spp. and Total Heterotrophic Bacteria (THB) in Litopenaeus vannamei (Pacific White Shrimp) Culture Farm Located in Velankanni Coast

Abstract

The present study assessed the population of Vibrio spp. and total heterotrophic bacteria (THB) in a semi-intensive Litopenaeus vannamei culture farm located along the Velankanni coast, Tamil Nadu, India. The investigation was carried out in four culture ponds during two consecutive culture periods, from February 2023 to June 2023 and from August 2023 to December 2023. Water, sediment and shrimp samples were collected on the 1st, 25th, 45th, 65th, 90th, 115th and 140th days of culture. Total heterotrophic bacteria were enumerated using Zobell’s marine agar, whereas Vibrio spp. were enumerated using thiosulphate citrate bile salts sucrose agar. Bacterial loads increased with the progression of culture days in both culture periods, and sediment samples generally recorded higher bacterial counts than water and animal samples. The highest THB counts in water, sediment and shrimp samples were 9.5 × 10⁷ CFU/ml, 4.3 × 10⁸ CFU/g and 9.8 × 10⁵ CFU/g, respectively, all in pond C during the first culture period at 140 DOC. Vibrio spp. also increased with culture duration, with the highest counts recorded in pond C during the first culture period. Pond C showed elevated Vibrio counts and was associated with White Feces Syndrome, reduced survival and lower average body weight. The findings indicate that regular monitoring of bacterial load, particularly Vibrio spp., is important for microbial management in L. vannamei culture ponds.