Existing lice modelling forces unnecessary treatments on farm-raised salmon to the detriment of fish welfare says Mowi Scotland CEO Ben Hadfield.
The UK’s largest salmon producer, Mowi Scotland, has introduced an advanced sea lice modelling system as part of its approved application to expand post-smolt salmon production at its Loch Etive farm.
The initiative represents a significant step in the company’s efforts to enhance sea lice control, a critical challenge in sustainable salmon farming.
The sea lice distribution model, developed by Dr. Philip Gillibrand, Mowi’s Head of Oceanography and Environmental Monitoring, compares the continuous production of sea-grown rainbow trout to the production of salmon smolts in two crops annually with fallowing events in every year.
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Over-estimating
The initial validation of sea lice modelling in Loch Etive, which was done with the largest ever deployment of post smolt salmon (2.5 million), shows that the model has good accuracy, but still over predicted sea lice levels in the first five months of stocking.
Dr Gillibrand said: “We used a sea lice dispersal model to establish the connectivity between our farm sites in Loch Etive and neighbouring sites, and then combined that with a population dynamics model to predict the lifecycle of the lice on the farms and estimate the daily production of lice larvae. Both models include a degree of precaution, and the lice count data we are collecting will help fine-tune the models and improve the predictions in the future.”
Commenting on the initial validation of sea lice modelling, Ben Hadfield, COO Mowi Farming Scotland, Ireland, Faroes and Atlantic Canada, said: “The post smolt salmon looked excellent: perfect form, healthy gills and low sea lice levels. Our model has a strong correlation to lice epidemiology, but still over predicts to a reasonable level, due to the precautionary assumptions in line with the disciplines expected in environmental modelling such as the fact that we are not able to model the full extent of our farmed cleaner fish removing sea lice from our salmon.”
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Regulating the Scottish salmon farming industry
Sea lice modelling now forms a big part of regulation in Scottish salmon farming due to SEPA’s Sea Lice Risk Framework where the migration of wild salmon through salmon farming regions on the West Coast is modelled. This was first suggested by the salmon industry as part of the Salmon Interactions Working Group as a practical way of improving the relationship between the industry and wild fish interests.
Hadfield believes that a robust and validated model which predicts sea lice levels is an important part of the world leading aquaculture regulation but warns that it will take three to six years to do it properly and accurately, even with the intense resource deployed by Mowi Scotland in the case of Loch Etive.
He is also critical of what he describes as “ultra-precautionary and therefore unrealistic model architecture” that has been presented by wild fish ENGOs such as Wild Fish, Costal Communities Network and Fisheries Management Scotland, which recently gave evidence to Scottish Parliament.
Dissapointing
“I was disappointed to see Wild Fish and CCN state that sea lice levels were high and uncontrolled when the data shows they are at the lowest level for 20 years. I believe that this recent evidence was at best misleading and given with the express intent of damaging the salmon farming industry,” said Hadfield.
“Indeed, this was duly refuted by Charles Allan, the most senior operational regulator at the Scottish Government, who gave evidence to the Parliamentary Committee that sea lice were under control and at low levels.”
SEPA’s SLRF Screening Model shows that out of more than 220 operational salmon farms in Scotland only 19 have a theoretical risk.
On Fisheries Management Scotland (FMS), Hadfield believes that whilst both organisations agree that a robust and validated model is a major step forward, what FMS failed to say to the committee was unacceptable.
Current model is fatally flawed
“The current SEPA model over-predicts sea lice concentrations, possibly by a factor of 4-5, and uses a very low impact threshold which equates to detectable effects on wild salmon smolt behaviour but not levels that would induce high mortality. It assumes all salmon farm biomass is constantly at its maximum, which it is not and, crucially, it is yet to undergo full validation to remove layer upon layer of over precautionary assumption in order to attain a realistic correlation.
“If this is not changed, then it will overregulate and force unnecessary treatment of farm-raised salmon which will challenge the high welfare of stocks, which all salmon farmers work for daily. Not explaining this clearly and calling for an ever more precautionary and rushed approach is misleading and is designed to achieve an over prediction of impact. I fervently hope that this can be corrected in future sessions, and we can talk with confidence about the reality of conditions in the sea and how salmon farmers across Scotland understand and adapt their methods accordingly.”
