Project Slingshot vs the evidence: what its salmon farming campaign leaves out

Claim 01

Are Scottish salmon farms overcrowded?

Project Slingshot describes farmed salmon as living in crowded, dirty underwater enclosures and presents intensive production as incompatible with fish welfare.

Salmon farming does involve very large numbers of fish. Whether that amounts to overcrowding depends on stocking density and welfare outcomes, not on headcount. Scottish farms operate under standards and monitoring covering fish health, water quality and husbandry; RSPCA Assured's Atlantic salmon standards, for example, set stocking limits and requirements across the life cycle.

A photograph of a pen holding thousands of fish cannot show whether density is excessive. That needs data on biomass, water volume, oxygen, behaviour and health. Equally, meeting a numerical limit does not guarantee good welfare, and the right density for salmon is a legitimate scientific debate.

Claim 02

Are sea lice eating farmed salmon alive?

Sea lice feed on the skin, mucus and blood of salmon, and severe infestations cause lesions, stress and secondary disease. On that point the campaign is right.

The question is how typical its images are. Sea lice occur naturally in the sea, although farming concentrates hosts and can change parasite dynamics. Scottish farms must report weekly average adult female lice counts, and the Scottish Government's Fish Health Inspectorate carried out 84 sea lice inspections and 12 enhanced inspections in 2025. Those figures describe inspection activity; they do not mean every site was inspected or every problem resolved.

Severe infestations have happened. What the campaign does not provide is prevalence data showing that its most disturbing footage represents normal conditions across the sector.

Claim 03

Are salmon farms filling Scottish lochs with dangerous chemicals?

The campaign names formaldehyde, azamethiphos, emamectin benzoate and deltamethrin and links their use to harm to marine wildlife. Some of that concern is well founded: certain antiparasitic treatments can affect non-target species, especially crustaceans, which is why the Scottish Environment Protection Agency regulates discharges.

But the campaign groups together substances with different uses, exposure routes and rules. Formaldehyde is used against some fish-health problems; emamectin benzoate is an antiparasitic medicine; antibiotics treat bacterial infections. A substance can be hazardous while the actual risk depends on concentration, frequency, environmental fate and local conditions.

Project Slingshot cites more than 48,000 kg of formaldehyde used on Scottish farms in 2025, drawing on Animal Equality's analysis. That is a large quantity and warrants scrutiny. On its own, though, a total mass says nothing about concentrations in receiving waters, the number of sites involved or observed ecological effects. Nor is an authorised treatment automatically harmless; the test is whether use meets regulatory limits and monitoring shows surrounding ecosystems are protected.

Claim 04

Have farm chemicals polluted 45 Scottish lochs?

This figure has a real basis. In 2017, the investigative outlet The Ferret reported that SEPA monitoring between 2006 and 2016 had found pesticide levels in sediments breaching environmental quality standards across 45 Scottish sea lochs and coastal areas. The industry needs to take that seriously.

It is, however, a finding about a monitoring period that ended a decade ago. The campaign does not say whether those sites still breach standards, which substances remain or what recent assessments show.

Claim 05

Does a salmon farm produce as much waste as a town of 50,000 people?

Salmon farms release organic matter and nutrients from feed and fish metabolism, which can affect the seabed and water quality.

A comparison with a town needs its workings shown. Is it nitrogen, phosphorus, solids or organic matter? Based on one farm or average production? Is the town's sewage treated? Is it about emissions or their effects? A comparison can be arithmetically valid for one pollutant under narrow assumptions and still say little about overall impact. We could not trace the source of the figure the campaign uses.

Measurement choices cut both ways. A 2021 study in Nature comparing aquatic foods found that farmed salmon and trout used relatively little land and freshwater among fed aquatic species, while also showing trade-offs on nutrient emissions.

Claim 06

Are farmed salmon artificially dyed pink?

The campaign argues that farmed salmon are fed a synthetic pigment to make their flesh look the way consumers expect.

The pigment, astaxanthin, is real and its use is no secret; producers also use colour guides to keep flesh colour consistent. But astaxanthin is a carotenoid found naturally in marine food webs. Wild salmon get it from their prey; farmed salmon get it from feed, where its source and dose are controlled. In both cases, dietary carotenoids colour the flesh.

Its safety has been assessed by European regulators. According to reporting on its April 2026 renewal assessment, the European Food Safety Authority found no new evidence requiring it to revisit its earlier safety conclusions for the additive under authorised conditions of use. Whether consumers prefer natural or synthetic sources is a fair question. Presenting the practice as painting fish to disguise a defective product is not.

Claim 07

Did 35 million Scottish salmon die before slaughter?

The figure comes from reported mortality data: Animal Equality counted roughly 35.9 million deaths on Scottish salmon farms between January 2023 and October 2025.

The number deserves attention, but without the population at risk, the production cycles and causes of death, it is not a mortality rate. The Scottish Government's 2025 production survey offers one: 68.8% of smolts put to sea in 2023 were eventually harvested, up from 61.8% for the 2022 cohort. Not all the remainder died; the government's method also counts fish removed through culling, sampling, escapes and broodstock selection. Salmon Scotland separately reports 82.3% survival across marine farms in 2024, using a different method that should not be compared directly with the government figure.

Comparisons with other livestock need the same care. Piglet pre-weaning losses cover weeks; broiler mortality covers a short growing cycle; salmon spend well over a year in production, much of it at sea. Showing that other farmed animals also die would not make salmon losses acceptable. The more useful measures for salmon are cohort survival, monthly trends, causes of death and differences between sites and years.

Claim 08

Did the industry use 1,564 kg of antibiotics in 2024?

Yes. The figure appears in Salmon Scotland's corrected reporting for 2024.

What the campaign leaves out is that the same reporting shows antibiotic use falling 67% from 2023, to 8.15 mg per kilogram of salmon produced, and that around 8% of farms needed antibiotic treatment in 2024 (7.1% of seawater sites and 10.6% of freshwater sites).

The government's own figures add a complication. The Veterinary Medicines Directorate publishes a separate estimate for salmon in its UK-VARSS report, but the 2024 edition was amended after publication and the two datasets differ in scope, including how freshwater and seawater stages are counted. Neither total should be treated as definitive until they are reconciled.

Antibiotic use is not in itself evidence of poor practice; treatment can be necessary for animal health. Overuse can drive antimicrobial resistance, which is why both the quantity and the trend matter. Antibiotics are also a separate question from antiparasitic treatments and from residues in the finished product.

Claim 09

Is salmon farming driving wild salmon towards collapse?

Interactions between farmed and wild fish are a legitimate scientific concern. Sea lice transfer, escapes and genetic effects have all been studied and require prevention and management.

The campaign's claim, though, is causal, and wild Atlantic salmon face many pressures: falling survival at sea, climate change, degraded rivers, barriers, predation and pollution. Aquaculture's risks belong in that wider picture rather than standing in for it.

The campaign cites sea lice infection pressure rising by up to 73 times. That figure comes from a 2005 study of juvenile pink and chum salmon migrating past a farm in British Columbia, Canada. It demonstrated an important mechanism for farm-to-wild transmission, but it did not measure Scottish Atlantic salmon, and different species, ecology and management limit how far it applies here.

Escapes are a genuine risk. In October 2025, around 75,000 salmon escaped from a Mowi farm in Loch Linnhe during Storm Amy. What that means for wild stocks depends on where escapees go, whether they survive and breed, and how they interact with wild fish.

Claim 10

Is Scottish salmon controlled by foreign corporations?

Largely, yes. Production is concentrated in a small number of large companies, several of them part of international groups.

But where a company is owned and where it creates economic activity are different questions. Farms employ local staff; boats need crews, nets need maintenance and sites depend on suppliers and contractors. The official production survey counted 1,410 people in seawater salmon production in 2025, a narrow figure that excludes processing, distribution and supply-chain jobs. The BiGGAR Economics study for Salmon Scotland estimates the wider sector supported 10,850 jobs and £953 million in gross value added in 2024. Jobs supported and value added are not the same as net benefit once alternative uses of capital, labour and coastline are counted, and the study was commissioned by the industry. That activity is still real, as are exports worth £828 million in 2025, according to HMRC data analysed by Salmon Scotland.

The campaign's focus on foreign ownership also sits awkwardly with its own funding. Project Slingshot is registered as a non-profit in the United States, and according to Fish Farming Expert its principal backers include the US-based Karuna Foundation and Coefficient Giving. That does not undermine its arguments. But if foreign funding does not delegitimise an advocacy group operating in Britain, foreign ownership alone should not erase a business's contribution in Scotland. What matters for both is what they do and how accountable they are.

Claim 11

Are taxpayers simply subsidising profitable multinationals?

Project Slingshot calls for an end to public money for industrial salmon farming and highlights grants to major producers.

Those grants exist. Scottish Government information releases document support under schemes including the European Maritime and Fisheries Fund and Marine Fund Scotland, and whether they are justified is a fair debate. But purpose matters. A 2026 review by the Sustainable Aquaculture Innovation Centre (SAIC) and Salmon Scotland identified 268 publicly supported innovation projects worth more than £183 million since 2018, over £83 million of them focused on fish health and welfare.

That does not prove every grant delivered value, or that profitable companies should automatically qualify. It does show that funding a technology to cut parasite-related welfare problems is a different proposition from subsidising operating profits. The right test is whether support delivers measurable public benefit: better welfare, environmental performance, innovation or regional jobs.