INFORMATION obtained from SEPA by the Salmon & Trout Association Scotland (S&TAS) shows that nearly one in five fish farms using Slice as a sea lice treatment show chemical residues in excess of Environmental Quality Standards.
Data from 146 farms which used Slice (emamectin benzoate) between January 2011 and September 2012 were obtained by the S&TAS.
At 28 of those farms (19.1%), Environmental Quality Standards were breached . The results are broadly in line with an earlier study by the S&TAS, which was based on data obtained under freedom of information data covering 2005-2010.
At the time, the Minister responsible, Stewart Stevenson MSP, stated that "should an EQS for sea louse chemicals be breached following the use and discharge of the substances to treat sea lice at fish farms, SEPA would take various steps to rectify the situation - for example, through a variation of licence conditions limiting the further release of these substances until residue levels reduced to below those identified safe levels."
Matters do not, however, appear to be improving and, to date, the S&TAS is unaware of SEPA varying the conditions of any fish farm licence to reduce chemical residues in line with Stevenson's assurance.
Fifteen of the 28 fish farms with samples in breach of Environmental Quality Standards for Slice are operated by Marine Harvest (Scotland) Limited.
Although Marine Harvest is the biggest operator in Scotland of salmon farms and is shortlisted for the Stewardship Award at tonight's Crown Estate-sponsored "Marine Aquaculture Awards 2013", this is a higher than expected number of breaches from their farms. The S&TAS queried this with SEPA who replied that "the results are unlikely to be impacted by an artefact of the reporting or recording process".
The reasons for the apparent problem associated with Marine Harvest fish farms is not known but one possibility, according to S&TAS, might be that efforts being made by Marine Harvest to reduce on-farm lice numbers are having the unwelcome consequence of increasing the chemical residue in sea lochs.
This would be a problem for wild crustaceans, which are particularly susceptible to Slice, and therefore also to lobster, crab and creel fishermen operating in the loch systems where salmon farms are using emamectin benzoate.
Hughie Campbell-Adamson, Chairman of the S&TAS, said: "What this shows is that not only is SEPA yet to get control of the chemical residue issue, but the apparent issue at Marine Harvest farms, which of course is yet to be bottomed out, could be due to efforts being made to control sea lice on the farmed fish.
"If it does turn out to be the case that efforts to control sea lice are having a negative effect elsewhere, it may be impossible in practice to adequately control sea lice on very high tonnage fish farms, down to a level which does not cause an unacceptable parasitic load on wild fish, while at the same time avoiding a threat to wild crustaceans, such as lobster, prawn and crab, upon which many inshore fishermen rely for their livelihoods.
"The answer is clear. Again, the S&TAS would urge both Marine Harvest and the Scottish Government to start the move towards closed containment of all salmon farming."