Scientists seeking fish with ‘bold’ personalities to clear away parasites

Fish with “bold” personalities are being sought by scientists in a new study aimed at helping clean up parasite problems in the aquaculture industry.

Researchers hope to single out the bravest Ballan wrasse from more timid members of their shoals to create breeding stocks instinctively suited to picking sea lice off farmed salmon.

Sutherland-based fish farming firm Loch Duart and Otter Ferry Seafish, of Tighnabruaich, are to work with researchers from Stirling University and the Sustainable Aquaculture Innovation Centre (SAIC) on the year-long project.

Ballan wrasse have been used by the industry for a number of years as “cleaner fish” in efforts to develop a natural solution to sea lice problems in fish farm pens around the Highlands and islands.

The new study will involve a series of tests to determine whether the boldness of individual fish makes them more adept at eating the parasites off salmon.

Researchers will monitor the behaviour of the wrasse by introducing a new object into their tank.

Video tracking the individual cleaner fish, they will then monitor their reactions to the objects and correlate the findings with how they later perform when introduced to farm pens.

Professor Herve Migaud, of Stirling University’s Institute of Aquaculture said: “Ballan wrasse are very special fish – they are very clever and demonstrate fantastic behaviour. If you walk by a tank, they will take an interest in you and physically watch you and follow.

“Each has their own personality and we want to correlate which traits – namely boldness and shyness – translate into Ballan wrasse being reliable and effective at delousing salmon.

“Cleaner fish are reared in hatcheries in controlled conditions and will not have seen salmon or sea lice in their life – but if we can identify the ones that are instinctively bold, we can use these to create breeding stocks that are more naturally suited to the job of being a cleaner fish.

“The wider project will inform how we create the best possible conditions to promote interaction between salmon and Ballan wrasse to reduce the prevalence of sea lice.”

Lewis Bennett, cleaner fish manager at Scouriebased Loch Duart, said: “Wrasse have been an integral part of our production since 2014 and they have provided the business with a strong performance platform to grow salmon as naturally as possible.

“The natural behaviour of the wrasse isn’t taught, nor is it forced, but it is allowing the animal to express their natural behaviour in a comfortable setting and under the full care of our site teams.

“The future to getting results at sea are to be reflected in the care, welfare and understanding of the individual species.

“This directly points to improved systems at sea and innovations to welfare and care of the fish.

“The Aquawrasse project is a great example of an academic study providing key information for industry practical application.

“The main focus for Loch Duart is to more accurately identify the behavioural traits, movements and annual differences in wrasse behaviour – from this we can then make changes to integral parts of our operations.”

BREEDING: A study has been launched to identify “bold” Ballan wrasse to use as “cleaner fish” at salmon farms.