Aquaculture is one of the fastest growing animal protein industries in the world, playing an important role in addressing food security and boosting global economies [1], projected to provide 106 million tons of seafood for human consumption by 2030. The ongoing shift from traditional farming to more intensive production practices leads to many challenges, including increased incidence of opportunistic infections and spread of antimicrobial resistance (AMR), as antibiotics are commonly used for prophylactic and therapeutic purposes [2,3]. Resistant pathogens have been found in commonly cultured fish and shellfish linked to reduced productivity and heightening public health concern associated with AMR transfer. The emergence of resistant opportunistic pathogens is a complex One Health issue, requiring innovative infection control and treatment approaches. Bacteriophages, viral predators of bacteria, can potentially offer a new ‘ecological’ solution to this problem [4]. In this project, we isolated bacteriophages against Vibrio harveyi and Vibrio alginolyticus, common opportunistic pathogens of fish, shellfish and humans [5]. Isolation was performed by co-incubation of bacteria with environmental specimens (i.e. sewage, prawn meat, pallial juices) and plaque picking on marine agar and tryptic soy broth supplemented with salt. Five phages with lytic activity against V. alginolyticus were purified; three, P1.1 (58 kb), P1.5 (64 kb), and Fc (52 kb), showing high lytic activity (1010-1011 PFU/mL) both in solid and liquid media. Host range testing of P1.1, P1.5, and Fc against the larger Vibrio collection showed cross-reactivity and synergistic effect on bacterial clearance. This work provides evidence of the presence in the environment of lytic phages that could be used for antibacterial application against major marine pathogens.