Epidemiological tracking and control strategies of early mortalities in hatchery-reared gilthead seabream (Sparus aurata) larvae

Abstract

Abstract Implementing competent biosecurity strategies is a key factor for maintaining a disease-free aquaculture. Bacterial infections are an eminent threat to all live stages occurring in the marine hatchery. Live foods, including algae, rotifers, and artemia, are potential sources of microbial infections in hatcheries with ineffectual biosecurity plans. In the present study, epidemiological, bacteriological, molecular, and histopathological investigations were carried out on all critical live components of the marine hatchery, including batches of algal cultures, rotifers ( Brachionus plicatilis ), artemia ( Artemia salina ), eggs, cultured gilthead seabream ( Sparus aurata ) larvae, and other inanimate components such as water supply. Clinically, fish larvae had pale skin and exhibited sluggish and frequent erratic swimming patterns. Two Vibrio isolates were presumptively identified by using the API 20E system. After molecular screening and phylogenetic analysis, these isolates were confirmed to be V. alginolyticus and V. vulnificus . Remarkably, V. alginolyticus was the most commonly recovered species from seawater, eggs, algae, rotifers, and artemia cultures. Both of these Vibrio isolates exhibited diverse sensitivities to different antibiotics used in the antibiogram, with maximal susceptibility to florfenicol. Therapeutic and preventive programs were imposed at different rearing stages after tracing the potential sources of infection.