Scottish salmon farmers are unhappy that sea lice "from marine fish farms" are being focused upon by SEPA. The agency has twice confirmed that sea lice from salmon farms are not responsible for the decline in wild salmon, they say.

Salmon sector challenges sea lice inclusion on SEPA hit list

Parasites 'from marine fish farms' among watchdog's seven significant water management issues

Gareth Moore Gareth Moore Gareth Moore editor
Published

Fish farmers have expressed disappointment that Scotland’s environment watchdog has included “sea lice from marine fish farms” in a list of seven “significant water management issues” facing the country.

The Scottish Environment Protection Agency (SEPA) has launched a public consultation about the issues that it seeks to tackle in its fourth six-year river basin management planning (RBMP), which will be finalised in December 2027.

As well as sea lice, the other areas of concern for SEPA are:

  • rural diffuse pollution (e.g.: agricultural run-off) 
  • the physical condition of rivers 
  • artificial barriers to fish migration (dams, etc) 
  • water use (managing it within environmental limits)
  • wastewater and sewer networks 
  • chemicals in the water environment 

SEPA says artificial barriers and lice from salmon farms are both a threat to wild fish populations.

Additional information

“In sufficient concentrations, sea lice can have a significant adverse impact on [wild salmon and sea trout]. We currently assess and manage the risk posed by sea lice to wild salmon and sea trout when determining applications for proposed new marine fish farms or to increase the permitted maximum biomass of fish held at existing fish farms,” says SEPA in a press release.

SEPA model 'wrong by a factor of 4 or 5'

Scotland’s salmon farmers say that SEPA’s modelling of salmon lice encountered by wild salmon smolts and sea trout substantially overestimates the number of the parasites in the sea.

Last year, Ben Hadfield, chief operating of Scotland’s biggest salmon farmer, Mowi Scotland, said: “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.”

“We now need to focus on gathering additional information necessary to understand the effects of sea lice from existing marine fish farms on wild salmon and sea trout. We expect this will involve several years of data gathering. Where the evidence collected shows significant adverse impacts on wild salmon or sea trout, we will ensure appropriate and targeted action is taken to reduce pressure from sea lice as part of the RBMP programme of measures and so help improve the condition of wild salmon or sea trout.”

A spokesperson for trade body Salmon Scotland said: “It is disappointing that the latest of many SEPA consultations includes a focus on sea lice.

“SEPA have twice confirmed, as recently as last year, to the Scottish Parliament that sea lice from salmon farms are not responsible for the decline in wild salmon. 

Inconsistent approach

“This focus is also inconsistent with the Scottish Government’s own wild fish strategy which identifies more than 40 other pressures on wild fish. 

“We trust that SEPA’s final plans will remain focused on the core areas where regulation can deliver the most meaningful improvements to Scotland’s water environment.

“Healthy freshwater and marine environments are critical to salmon farming, and many of the issues raised in the consultation have the potential to affect those environments. 

“Scottish salmon farmers already operate to some of the highest health, welfare, and environmental standards in the world, with sea lice levels now among the lowest on record.”

Wild fish decline 'not due to lice'

Two SEPA executives have separately told Scottish Parliament committees that the decline in wild salmon in Scotland is not due to sea lice from salmon farms.

In November 2020 Peter Pollard, head of ecology at SEPA, told members of the Rural Economy and Connectivity (REC) Committee: “Do we think that sea lice from farmed fish are responsible for the declines that we have seen over the decades in wild fish? No.”

Last year Lin Bunten, chief operating officer, regulation, business, and environment at SEPA, told the REC Committee’s successor, the Rural Affairs and Islands Committee: “I am not aware of a direct link between farmed salmon and wild salmon per se. However, the salmon interactions working group has identified sea lice as a potential impact, which is why we brought in the framework at the beginning of February”.

In a press release today, SEPA said its consultation report – Safeguarding Scotland’s Water Environment - outlines the targeted work already under way to address significant water management issues and sets out a recalibrated approach to achieving further progress with partners.

It added that input from members of the public and communities is essential to ensure plans reflect local experiences, practical solutions and a wide range of perspectives across Scotland.

Proposals 'at formative stage'

Rachel Harding-Hill, head of environmental resilience and enhancement at SEPA, said protecting and improving the water environment requires ongoing effective management of the issues that are having a negative impact in a catchment-wide approach. 

“Our current proposals are at a formative stage, and we want to gather valuable evidence of the range of experiences and opinions, knowledge and ideas on this pivotal issue to inform our decision-making. 

“We know people across Scotland share our respect and aspirations for our water environment and we look forward to engaging with them at this key stage of our planning.”

The consultation runs from today until March 3, 2026, and will feed into Scotland’s River Basin Management Planning (RBMP) which will be further consulted on in December 2026. The current RBMP cycle ends in December 2027. 

Take part in the consultation here.

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