<![CDATA[Vibrio outbreaks pose a severe threat to intensive pacific white shrimp (Litopenaeus vannamei) aquaculture, necessitating effective waterborne biocontrol strategies. This study evaluated the efficacy of a commercial multispecies probiotic formulation on the dynamic abundance of Vibrio spp. within the centralized inlet and outlet channels of an intensive shrimp farm. A field-based observational monitoring was conducted weekly for four weeks. Total Vibrio Count (TVC), Vibrio alginolyticus, Vibrio parahaemolyticus, and water quality parameters (pH, DO, salinity) were quantified from surface water samples. The outlet channel consistently exhibited a significantly higher TVC than the inlet, acting as a microbial accumulation zone. Following twice-weekly probiotic application, Vibrio alginolyticus in the outlet decreased from 3.87 to 3.41 log10 CFU/mL due to rapid competitive exclusion. Conversely, Vibrio parahaemolyticus demonstrated greater resilience, showing a temporary nutrient-induced bloom in Week 3 (2.67 log10 CFU/mL) before declining significantly to 1.77 log10 CFU/mL by Week 4, indicating a slower, time-dependent suppression mechanism. Non-target Citrobacter freundii remained unaffected due to innate outer membrane resistance. Environmental fluctuations, particularly suboptimal salinity and pH in the effluent, acted as synergistic stressors that enhanced probiotic competitiveness. Multispecies probiotics are highly effective yet strain-specific biocontrol agents. Continuous dosing combined with centralized effluent treatment is essential to prevent pathogen discharge into the surrounding marine environment.]]>
