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Scotland’s salmon farming industry is planning to use a toxic pesticide banned in terrestrial agriculture because of dangers to bees, campaigners are warning.

They have condemned the secrecy surrounding the pesticide as “scandalous” and expressed fears it could damage marine wildlife.

The industry, however, says pollution will be removed by a new filtration system. The Scottish Government describes the system as “potentially ground breaking” and says it should be trialled in Scotland.

In the past fish farming companies have used different pesticides to try and kill sea lice that plague caged salmon. But several have ended up being banned or withdrawn because of the damage they did to the environment – or because they became increasingly ineffective as lice developed resistance.

In a series of investigations published in 2017, The Ferret revealed that the Scottish Government and its Scottish Environment Protection Agency (Sepa) had secretly bowed to industry pressure not to ban the latest anti-lice pesticide, emamectin, which was marketed as Slice.

Then, in November 2018, Sepa published evidence that emamectin was harming wildlife and more widespread than previously thought. It promised tougher restrictions on the chemical.

Now the industry has a new pesticide it wants to try. It is called Ectosan or BMK08, and it is designed to be used with a new water purification technology known as CleanTreat.

The industry, Sepa and the Scottish Government have all declined to name the key ingredient of Ectosan. But an industry application in Norway published online by the Aquaculture Stewardship Council, an international organisation that certifies farmed fish, states that Ectosan contains a chemical called imidacloprid.

Imidacloprid is one of three nicotine-based pesticides known as neonicotinoids which were banned by the European Commission in 2018 for all outdoor use on plants. The chemical “could no longer be considered safe due to the identified risks to bees,” the commission said.

According to US government scientists, imidacloprid is an “environmental hazard” which can be “very toxic to aquatic life with long lasting effects”. In 2017 the Rivers Trust, which brings together more than 60 local groups in England, Wales and Ireland, warned that contamination from the chemical, along with other neonicotinoids, endangered insects, birds and fish in rivers.

CleanTreat is described by its manufacturers, Benchmark, as a “closed treatment system” which removes pollutants from water before it is released into the sea. It has been trialled in Norway but – according to the industry and the government – not so far in Scotland.

Emails released to campaigners under freedom of information law show that fish farming companies lobbied Scottish ministers in 2019 to allow trials of CleanTreat. They were supported by the rural economy minister, Fergus Ewing, who backed a company bid to “speed things up”.

Sepa has also disclosed that it had five meetings about CleanTreat with Benchmark, one in 2018 and four in 2019. Industry reports suggest that Benchmark is preparing to make applications to regulators in different countries to license the technology.

Shame on Sepa and the Scottish Government for protecting commercial confidentiality rather than the environment. Don Staniford, Scottish Salmon Watch

Campaigners have criticised the secrecy over Ectosan, and called for full transparency. “Once the public find out about dirty secret of imidacloprid, Benchmark’s CleanTreat system will be dead in the water,” said Don Staniford, from Scottish Salmon Watch.

“The abject failure to inform the public – including fishermen, shellfish farmers and tourist operators – about the use of such a toxic chemical is scandalous.”

Staniford has been waging a prolonged freedom of information battle with the Scottish Government and Sepa to find out more about Ectosan. He is also demanding to know whether the chemical has already been used by fish farming companies.

“Shame on Sepa and the Scottish Government for protecting commercial confidentiality rather than the environment,” he told The Ferret.

“Given the toxicity of imidacloprid and the controversy over neonicotinoids, it is not surprising that Benchmark wanted to keep the ingredients of Ectosan – renamed BMK08 – top secret. Silence speaks volumes.”

The wild fish campaign group, Salmon and Trout Conservation Scotland, called for fish farms to be kept apart from the marine environment. “The need to treat for sea lice, with whatever toxic chemical the industry alights on next, completely disappears if the industry moves into closed containment,” said the group’s solicitor, Guy Linley-Adams.

“Until it does that, the chemical arms race against sea lice will continue, will continue to be lost, and the damage to the marine ecosystems caused by fish farms will just get worse.”

Linley-Adams urged Sepa to demonstrate how CleanTreat would be “rigorously monitored” and properly used before any environmental discharges were licensed.

The Scottish Greens were also worried. “I’m very concerned that a pesticide that has been banned for use on the land looks set for approval for use in fish farming,” said the party’s environment spokesperson, Mark Ruskell MSP.

“There is a startling lack of transparency, with Fergus Ewing always ready to approve the next sticking plaster approach to the chronic animal health and welfare issues caused by the industry.”

Benchmark told The Ferret that “due to regulatory requirements we are restricted as to what information we can share publicly on our new sea lice medicine, BMK08.” The company said that “at this time” it had no trials scheduled in Scotland.

“We take environmental care extremely seriously and it is at the heart of our CleanTreat system,” said a company spokesperson.

“BMK08 will only be used together with our closed water purification system, which removes any medicine from the treatment water before being released into the sea.”

The Scottish Salmon Producers’ Organisation (SSPO), which represents fish farming companies, pointed out that any potential chemical would have to undergo a “rigorous environmental appraisal” before it was allowed to be used.

“The SSPO supports the trial of innovative new solutions like this one which is designed to remove medicinal residues from the water,” said a spokesperson for the organisation.

“This is in-line with the sector’s holistic approach to managing the health and welfare of our fish while minimising the impact of medicine use within the environment.”

A Scottish Government spokesperson said: “This is a potentially ground breaking treatment which has been developed in Scotland and which should also be trialled in Scotland with relevant and appropriate safeguards and monitoring in place.

“Aquaculture and its wider supply chain helps contribute £620 million every year to Scotland’s economy, with farmed salmon being Scotland’s number one food export. The sustainability and good health of farmed salmon is therefore essential, and we recognise the need to protect Scotland’s environment on which the sector depends.”

The government spokesperson added: “No licence applications have been received for any sea trials of CleanTreat or Ectosan.”

The Scottish Environment Protection Agency pointed out that it controls and advises on discharges to ensure that environmental standards were maintained. “We are happy to provide advice to any company looking to reduce discharges of medicine residues using effluent treatment systems, including to Benchmark,” a Sepa spokesperson said.

“Trials of any new medicine that would involve a discharge of residues into the environment would require authorisation. Discharges into the sea from land or from fish pens require a permit from Sepa.”

The spokesperson added: “Discharges from vessels, such as well boats, require a permit from Marine Scotland. Sepa has not issued a permit to Benchmark or any other company to discharge any new sea lice medicine for use on marine finfish farms, nor are we in receipt of any application to discharge a new sea lice medicine for use in marine finfish farms.”

Photo thanks to iStock/Julian Dewert.