Abundance and spatial patterns over time of Vibrionaceae and Vibrio harveyi in water and biofilm from a seabass aquaculture facility

International audienceOne of the major threats to the seabass (Dicentrarchus labrax) aquaculture sector is the development of vibriosis, a disease caused mainly by bacteria from the family Vibrionaceae, especially Vibrio harveyi. This disease can result in important economic losses or severe public health problems. Furthermore, bacteria can form biofilms on the walls of aquaculture tanks, leading to the persistence of potentially pathogenic bacteria on fish farms. Given the relationship between abundance in the surrounding environment and prevalence in fish, monitoring the presence of V. harveyi in rearing water and biofilms over time may help better understand the dynamics of the pathogen and factors that increase the risk of vibriosis outbreaks. In this study, the dynamics and spatial patterns of cultivable Vibrionaceae and V. harveyi in water and biofilms from rearing tanks and in the cold-and hot-water inlets supplying the farm were monitored for 7 months. Several potential seabass pathogens were isolated: Photobacterium damselae , Vibrio alginolyticus , V. harveyi , Vibrio owensii and Vibrio rotiferianus. However, V. harveyi remained the most problematic pathogen. Its relatively constant presence in water and biofilm samples throughout the sampling campaign represents a risk for vibriosis outbreaks. Moreover, the correlation between water temperature and the abundance of V. harveyi suggests that the risk fluctuates throughout the year. Obtaining qualitative data regarding the relative diversity of viable culturable Vibrionaceae and quantitative data on the abundance of V. harveyi over time in a seabass aquaculture facility is the essential first step for designing new solutions to manage vibriosis