UK researchers develop tool to improve salmon “cleaner fish” welfare
Researchers at the University of Stirling have developed a new tool that fish farmers can use to improve the welfare of lumpfish, a species crucial to tackling the problem of sea lice in salmon.
Lumpfish are increasingly being used by the salmon industry as a “cleaner fish” to remove parasitic sea lice, which cost the Scottish salmon industry alone an estimated £40 million (US$55.6 million) per year.
Because lumpfish are a relatively new fish to aquaculture, researchers are still establishing the optimum conditions for the species’ welfare.
In a new study, a team led by Dr Sonia Rey Planellas at the University of Stirling’s Institute of Aquaculture has established the correlation between lumpfish growth weights and welfare, and turned it into a tool farmers can use to assess the health of the fish and take remedial action if required.
“At the moment, in the UK we use operational welfare indicators (OWIs) for fish welfare,” Dr Rey Planellas said, “but lumpfish are a different shape to many other fish, so it’s about identifying the best indicators for each species.”
The researchers developed four indices based on weight and length comparisons, correlated with the OWIs for lumpfish, to develop a formula that calculates an overall score of above or below 2.8 (for other fish the figure is 3). Above 2.8 means the fish is fine, below means the condition is sub-optimal and farmers must take remedial action.
Farmers will then input their measurements into a free online tool.
“It can help farmers calculate optimal times to introduce the lumpfish to the salmon, for example,” said Dr Rey Planellas. “Lumpfish can sometimes grow very fast, which leads farmers to introduce them too early, when the waters are still too cold. This is not good for welfare outcomes.”
“This tool will help farmers identify fish that are below average condition for the population in the cage, and will indicate a need for prompt, remedial action, such as modifying feed,” said Jim Treasurer, a scientist with Fai Farms near Fort William who worked on the study and works closely with fish farmers.
“The welfare indicators identified from the project have since been adopted at those of our farms using lumpfish to help control sea lice levels and have proven hugely helpful in ensuring high welfare standards among our cleaner fish,” added Ralph Bickerdike, Head of Fish Health and Welfare at Scottish Sea Farms who participated in the study.
The researchers collected data from 456 fish from two different environments: a hatchery at Ardtoe in Scotland and in salmon sea cages in the Faroe Islands and Scotland, in conditions approved by the University of Stirling’s Animal Welfare and Ethical Review Body.
The project was a collaboration between the University of Stirling, including modelling by lecturer Bruce McAdam; the Scottish Aquaculture Innovation Centre (SAIC); the Fisheries Society of the British isles (FSBI) and several salmon companies. Its focus was to improve non-medicinal measures to manage sea lice.
“The main idea is to minimise the use of medicines in salmon farming,” Dr Rey Planellas added, “and cleaner fish offer a good alternative. However, we need to develop our knowledge of the welfare of these animals.”