Vibrio load and percentage composition of sucrose‐fermenting vibrios in Nile tilapia (Oreochromis niloticus) cultured in brackish water earthen ponds and biocontrol potential of recycled tilapia‐conditioned greenwater against population growth of V. parahaemolyticus and non‐sucrose‐fermenting vibrios in the grow‐out culture of white leg shrimp (Litopenaeus vannamei)

Abstract

<i>Vibrio</i> are known opportunistic pathogens of pond-cultured fish and shrimp. This study determined the presumptive <i>Vibrio</i> count (PVC) and percentage composition of “beneficial” sucrose-fermenting vibrios (SFVs) and “pathogenic” non-SFVs in the water, sediment, gills and intestines of healthy tilapia <i>Oreochromis niloticus</i> collected every 2 weeks from Days 30 to 120 post-stocking in brackish water earthen ponds. PVCs in water and sediment ranged from 10²–10⁴ CFU/ml/CFU/g while in tilapias' gills and intestines, PVCs ranged from 10³–10⁶ CFU/g and 10²–10⁶ CFU/g, respectively, with SFVs dominating in water, sediment, gills (≥50%), and intestines (≥80%) of tilapia. Because use of tilapia-conditioned green water (TCGW) for shrimp's grow-out culture has been reported effective against acute hepatopancreatic necrosis disease outbreaks caused by <i>V. parahaemolyticus</i>, PVC, SFVs/non-SFVs (%), and <i>V. parahaemolyticus</i> count (VPC) in the recycled TCGW and <i>Litopenaeus vannamei</i>'s hepatopancreas were also examined from stocking until 105 days of culture (DOC) in earthen ponds. PVCs ranging from 10²–10³ CFU/ml and 10³–10⁴ CFU/g were noted in water and shrimp's hepatopancreas, respectively. While non-SFVs population in water varied, a downward trend typified by an abrupt 50% reduction was noted in hepatopancreas at DOC 42, and remained or further dropped until DOC 105. VPCs in water likewise varied (undetectable–10² CFU/ml) while in hepatopancreas, counts dropped to undetectable level from DOC 70 onwards. Current data illustrate that remarkable shift of SFVs' dominance in the water and concomitantly in shrimp's hepatopancreas, plays a pivotal role in regulating non-SFVs proliferation in shrimp's hepatopancreas via competitive exclusion.