Lumpfish and Ballan wrasse have their own welfare issues, which should not be ignored.

Fish species such as lumpfish and Ballan wrasse, are increasingly being used as cleaner fish to help control the numbers of sea lice in salmon and trout pens.

Of course, the cleaner fish themselves also have welfare issues. They cannot survive on sea lice alone, and can suffer high rates of mortality when simply placed in a salmon pen without a proper feeding and welfare regime. Clearly, tackling one welfare (and ethical) challenge is not helpful if it simply creates another problem.

Harvesting wild wrasse and lumpfish for this purpose also depletes fish stocks, so these species are now also being farmed. Unlike salmon, for example, which have been domesticated for 50 years, lumpfish and wrasse have been farmed for a much shorter time and there are still gaps in the industry’s knowledge about them.

A checklist for health

A group of researchers at Swansea University, including Professor Carlos Garcia de Leaniz, Chair in Aquatic Sciences and Biosciences, drew on the expertise and experience of participants from the fish farming sector, animal welfare, academia and regulators to assess consensus on the main challenges and potential solutions for lumpfish welfare.

The study (Addressing the welfare needs of farmed lumpfish: Knowledge gaps, challenges and solutions, July 2021) used a “Delphi” approach to see how the experts viewed the usefulness of five behavioural and 12 physical welfare indicators. The Delphi method is a quantitative, questionnaire-based technique that aims to identify a consensus among experts.

The researchers did indeed find a consensus, identifying for example that fin erosion and body damage were the most useful and practical operational welfare indicators, while blood parameters and behavioural indicators were seen as the least practical.

One thing that became clear was – to state the obvious – lumpfish are not Atlantic salmon. Applying a common set of welfare standards and standard operating procedures to both species, even if they are co-habiting in the same pens, is not likely to be in the interests of the cleaner fish.

The researchers also identified 16 practical solutions for improving the welfare of lumpfish. In summary, these are:

  1. Adopt welfare guidelines specifically developed for this species.
  2. Train staff in their use and implementation.
  3. Monitor fish often and look for early signs of poor welfare.
  4. Watch for underweight fish and adjust feeding rations, feed frequency and feed delivery accordingly.
  5. Monitor mortality rates regularly and investigate whether mortality exceeds the norm (defined by the median and the 10th-90th percentile historical benchmark 114).
  6. Keep densities within optimal values for the species, typically
  7. Screen-out lumpfish with deformed suckers at the earliest opportunity.
  8. Reduce potential disturbance and handling as much as possible.
  9. Provide shelters and cover in tanks.
  10. Check water quality regularly.
  11. Grade frequently, as adequate for the size and condition of the fish.
  12. Vaccinate against infectious diseases.
  13. Avoid areas with strong currents or outside the optimal thermal niche.
  14. Avoid prolonged transport whenever possible and check water quality during transport.
  15. Be prepared to cull fish with suboptimal welfare under veterinary advice.
  16. Slaughter lumpfish humanely.

Measure for measure

Meanwhile, researchers at the University of Stirling’s Institute of Aquaculture have also been addressing the lumpfish issue. Their conclusion is that measuring growth weight is a better indicator of health than commonly used indicators such as fin damage.

The Institute team also developed a new tool to assess lumpfish welfare, which should help fish farmers to detect problems and take remedial action where required.

Dr Sonia Rey Planellas at the Institute of Aquaculture has established a correlation between lumpfish growth weights and health outcomes.

She says: “At the moment, in the UK we use Operational Welfare Indicators (OWIs) for fish welfare, but lumpfish are a different shape to many other fish, so it’s about identifying the best indicators for each species.

“Fin damage is typically the indicator that is used, but in this study we found a more useful indicator was the correlation between growth weight relative to size and welfare.”

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 input their measurements into a free online tool.

“It can help farmers calculate optimal times to introduce the lumpfish to the salmon, for example,” says 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.”

Lumpfish are quite distinct from most farmed fish in terms of their body shape and behaviour, so the OWIs used to assess the health of salmon, for example, are not necessarily good indicators of cleaner fish health.

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 paper, Using model selection to choose a size-based condition index that is consistent with operational welfare indicators, is published in the Journal of Fish Biology.

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.

Jim Treasurer, a scientist with Fai Farms near Fort William, worked on the study. He says: “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.”

Ralph Bickerdike, Head of Fish Health and Welfare at Scottish Sea Farms, who participated, adds: “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.”

Ballan wrasse

Meanwhile a study by a group of researchers is aiming to determine the best possible conditions to help Ballan wrasse to grow and thrive.

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.

Otter Ferry Seafish, BioMar, Scottish Sea Farms, Mowi, and the Sustainable Aquaculture Innovation Centre (SAIC) are supporting the research, which could improve the robustness, welfare and resilience of Ballan wrasse when deployed into salmon pens.

Ballan wrasse display complex behavioural traits throughout their lifecycle, culminating in their sea lice foraging activity. Scientists believe hatchery processes during their early development may not only impact on their performance and welfare, but also their ability to become effective delousers at sea. Determining the optimal conditions – particularly as they grow in hatcheries – could be transformational for the sector’s approach to sea lice treatment. The outcomes of the research project could also be used to scale up hatchery production.

Professor Herve Migaud from the University of Stirling’s Institute of Aquaculture says: “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.

The private sector is also finding ways to help care for the cleaner fish. Feed companies have developed bespoke feeds for cleaner species – for example, World Feeds’ VAF Fee Blocks have been developed to provide a balanced diet, delivered in a formula that suits the cleaner fish’s natural grazing behaviour.

Meanwhile Norway-based Aquasolutions offers bespoke “recapture hides” to help with the efficient and gentle recapture of wrasse and lumpfish – recreating the kelp in which the cleaner fish like to shelter.

Cleaner fish play an important role in protecting farmed fish, but their own welfare should also be an important consideration.

 

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