Influence of temperature and spawning effort on Haliotis tuberculata mortalities caused by Vibrio harveyi: an example of emerging vibriosis linked to global warming

Since 1998, Haliotis tuberculata mass mortalities have been occurring regularly in wild abalone populations in France during their reproductive period and in conjunction with seawater summer temperature maxima and Vibrio harveyi presence. To confirm the importance of bacterial exposure, temperature and reproductive status on abalone susceptibility, experimental infections via bath exposure were performed using abalone ranging from immature to reproductively mature. Ripe abalone were more susceptible to the bacterium than immature specimens (P < 0.001), and a difference of only 1 degrees C in temperature had a highly significant impact on the mortalities (P < 0.001). The natural mortalities that were surveyed during summer 2007 confirmed that recent epidemic losses of European abalone appeared in conjunction with host reproductive stress, elevated temperatures and presence of the pathogen V. harveyi. In view of the elevation of the mean summer temperatures observed in Brittany and Normandy over the last 25 years, this temperature-dependent vibriosis represents a new case of emerging disease associated with global warming.