New case study: strengthening Ballan wrasse vaccination through collaborative research

Ballan wrasse play a key role in Scottish salmon farming as cleaner fish, helping manage sea lice in an environmentally responsible way. To reduce pressure on wild stocks, most wrasse now come from hatcheries, where they can also be vaccinated against naturally occurring bacterial diseases. One of the most significant of these is atypical Aeromonas salmonicida, which can still affect fish despite current vaccines. 

Building on earlier SAIC‑funded research, this partners in this project were Otter Ferry Seafish, the University of Stirling, Mowi Scotland and Ridgeway Biologicals. The project aimed to deepen understanding of how well vaccinated wrasse recognise and respond to different strains of this pathogen. The total value of this project was £94,792  

The team analysed blood samples from two commercial production sites to compare antibody responses, assess how broadly these antibodies recognise circulating bacterial strains, and explore whether they have any neutralising effect. 

Results showed that vaccinated wrasse produce antibodies that recognise multiple strains, although responses varied between fish and between hatcheries. Fish receiving an initial immersion vaccine appeared to develop a broader response, but further controlled studies are needed to confirm this. The project also advanced an ethical alternative to fish trials by using wax moth larvae to compare the virulence of different bacterial types. 

The full title of this project is ‘Evaluating immune response of vaccinated ballan wrasse (WraAs OptiVacc 2)’.  

Read the case study