Wild-caught and farmed ballan wrasse are used as cleaner fish.

Giving wrasse the right start

A group of researchers is aiming to determine the best possible conditions to prepare hatchery-produced ballan wrasse for life as cleaner fish in salmon farms.

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The project builds on more than 10 years of ballan wrasse research led by the University of Stirling’s Institute of Aquaculture and will explore a range of nutritional and environmental factors, such as the formulation of feeds and rearing conditions, to determine how they impact the health and welfare of the wrasse, which eat the lice that attach themselves to salmon.

Cleaner fish grower Otter Ferry Seafish, feed producer BioMar, salmon farmers Scottish Sea Farms and Mowi, and the Sustainable Aquaculture Innovation Centre (SAIC) are supporting the research.

Herve Migaud: Ballan wrasse behaviour can be significantly impacted by environmental factors.

A complex species

Professor Herve Migaud from the University of Stirling’s Institute of Aquaculture said: “Years of research have taught us that ballan wrasse are a complex fish species. Their behaviour can be significantly impacted by environmental factors from a very early developmental stage including the nutrients they are given, especially as they have a rudimentary digestive system without any stomach.

“In the wild, it can be a case of survival of the fittest, and the fish tend to develop a level of resilience that we are aiming to understand and recreate in a controlled environment. Exploring the impact of different variables in the hatchery process, in particular, can help us to create the best possible conditions to help the fish thrive and prepare them for when they are deployed into a salmon farm.

“The demand for cleaner fish is growing and the aim is to get to a point where we can meet the demand for healthy and effective hatchery-reared ballan wrasse and enable the sector to reach full reliance on farmed rather than wild cleaner fish in coming years, ultimately helping salmon farmers with a sustainable solution to sea lice.”


Researchers will also look at the nutrients in the feeds, such as vitamins and minerals, needed by ballan wrasse from the first feeding and weaning stages to support bone and cartilage health and minimise the risk of deformities, exploring the use of supplements, immunostimulants and functional feeds to improve resistance to bacterial disease. These will help to better prepare ballan wrasse for what they experience in the waters of a fish farm.

Anticipated benefits of the project include new guidelines for increased survival, welfare and robustness of farmed ballan wrasse in hatcheries as well as increased efficacy of delousing programmes, which could lead to a reduction in medicinal treatments. There is also potential to create new feed products for use in hatcheries.

Antonios Chalaris: Tailor-made feed.

Fine-tuning feed

Dr Antonios Chalaris, product manager at BioMar, said: “Over the last decade we have invested significantly in research to develop recipes that are tailor-made for the specific requirements of ballan wrasse, including our mild-extruded Symbio products which are already successfully being used in hatchery production and deployment.

“Gaining a deeper understanding of the needs of the species will provide valuable insights to help refine and fine-tune feed ingredients to support the fish to grow and thrive.”

Unlocking potential

Dr Thomas Cavrois-Rogacki, research and development and health manager at Otter Ferry Seafish, said: “Improving the performance and welfare of the ballan wrasse at the hatchery is one of the keys to unlocking the full potential of the species as cleaner fish.

“While early research on the species focused on increasing the numbers of fish produced, now is the time to focus on improving their quality, which is unconditionally linked to their ability to delouse and their resilience at sea. Furthermore, the expansion of the ballan wrasse culture has the potential to create new jobs in rural areas to support hatchery production and deployment at sea and to promote an eco-friendly, efficient and cost-effective approach to tackling sea lice.”