Variations of Vibrio Populations in Pacific White Shrimp, \u3ci\u3eLitopenaeus vannamei\u3c/i\u3e, Aquaculture Raceways

Reducing incidence of vibrioses in intensive aquaculture systems is essential to maintaining yields. This study performed real-time qPCR (quantitative polymerase chain reaction) using primers targeting 16s rDNA sequences for total bacteria, the Vibrio genus, and Vibrio parahaemolyticus in aquaculture tanks over the growing season. Total DNA concentrations in each sample were measured with a NanoDrop 2000 Spectrophotometer (Thermo Scientific, Inc. USA). These data were compared to two levels of bio-floc solids removal in addition to physical and chemical tank parameters such as temperature, ammonia, nitrite, nitrate and phosphate. The total bacteria gene copy abundances were higher (p = 0.0081) in the low solids tanks but the quantity of Vibrio genus and Vibrio parahaemolyticus DNA copy numbers did not significantly differ between treatments. Regressions performed between the bacterial populations, shrimp specific growth rate (SGR) and nutrient concentrations were found to support the concept that bio-floc in the high solids tanks processes nutrients and suppresses Vibrio populations. Optimizing the quantity of bio-floc is essential for controlling nutrient concentrations in order to select for beneficial bacteria that can improve shrimp health and growth. High nutrient concentrations can stress livestock and promote the incidence of disease causing bacteria and should therefore continue to be monitored and controlled