As Scottish fish farming grows, so does pesticide use

As salmon farming in Scotland increases so does the use of chemicals to kill parasites. Here’s the data that explains the chemicals used and how the levels have dramatically changed.

Scottish fish farms with negative environmental assessments from Sepa, and those with a clean bill of health, click above to see the full interactive map made by GreenInfo

For the first time, a full list of the chemicals used to control the sea lice parasite on every Scottish salmon farm has been disclosed after a freedom of information request to the Scottish Environment Protection Agency (SEPA). The data, requested by the campaigner Don Staniford who runs the website Fishyleaks, shows that overall use of pesticides by the salmon farming industry has increased each year, from 188kg in 2008 to 395kg last year – an increase of some 110%.

In that same period, salmon production increased more modestly, by some 22% to a forecast total of 157,000 tonnes last year.

Farmed salmon is now Scotland’s largest single food export, outstripping beef, dairy produce and wild-caught fish. Worth nearly £540m in 2010 to the producers, its global retail value is estimated to be well over £1bn, according to these figures from the Scottish Salmon Producers Association (SSPO). The industry and Scottish government hope to increase production by 50% by 2020, particularly to target new markets such as China.

Showing farm-by-farm usage, these figures are the voluntarily declared figures from each company: Sepa takes them on trust. These chemicals, designed to attack the parasite’s nervous systems or shells, were used 2,756 times. Environmentalists say the chief reason for the increased usage is to counter the increasing levels of resistance shown to these pesticides by sea lice, which damage farmed fish and threaten wild salmon and trout near fish-farms sites.

There is no direct link between salmon mortalities and chemical usage, but they do illustrate the sometimes high levels of wastage and loss. Deaths can occur for a variety of reasons, including natural events such as storms, to seal predation or very frequently diseases, and at various stages in a salmon’s life.

Usage of some, such as the agricultural pesticide cypermethrin – best known as a sheep dip – has fallen sharply from 21kg in 2008 to under 1kg in 2011. Year on year use of the four other compounds, deltamethrin, emamectin, teflubenzuron and azamethiphos, has fluctuated but has increased over time.

The organophosphate azamethiphos, described by Sepa as needing “great care” by fish farms “because even a slight overdose can harm or kill the fish”, now accounts for more than half of all chemical use by weight. Its usage had more than doubled since 2008, from 100kg to 211kg last year.

The Scottish Salmon Producers Organisation and Sepa insist there is no evidence or grounds to believe that this sharp rise in pesticide use poses a danger to the overall marine environment. “The effects of sea louse medicine residues on the environment are localised and relatively short lived. Therefore, assessing their impacts is best done on a local, site specific basis. Attempting to draw conclusions from national statistics on use and release of such substances, is a less efficient way of monitoring, because the gross mass of active ingredients discharged will vary considerably. This is due to a wide range of circumstances, not least because the dose rate, when using different medicines, is highly

However, Sepa admitted it did no national or regional monitoring of overall chemicals use, to establish whether there could be cumulative effects or wider policy issues. It said: “There has been no need for Sepa to make such a comparison. Sepa has collected data on chemical use and has undertaken work to evaluate its potential impact. Sepa collects the data on a site by site basis and assesses use at that level. Sepa does not collect or aggregate this into national data for use by the agency because doing so provides no useful outputs. However, reporting of this nature is required to fulfil legislative requirements of Scotland, the UK and EU.” However, environmentalists and critics of fish farmers say there is substantial evidence that numerous fish farms are failing to use these chemicals safely and that Sepa’s failure to do any Scotland-wide studies or to monitor overall pesticide use greatly weakens their position.

Guy Linley-Adams, a solicitor working for the Salmon & Trout Association aquaculture campaign, believes the underlying problem the industry faces with sea lice infestation is the critical issue. “It is a potential doomsday scenario for wild salmon is on the west coast. Scotland has an expanding salmon farming industry, increasingly unable to control the sea lice problem on its farmed fish, relying on chemical treatments to which the lice are becoming tolerant or resistant and still largely in denial about the impact they are having on the wider marine environment.”

Data summary

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