11 June 1997

SEPA has a duty to ensure a sustainable, long-term future for the environment and local economies in Scotland. In the longer term, SEPA does not believe that the use of ever more powerful chemicals to control sea-lice infestation is the way forward for the salmon industry. However, SEPA has a statutory duty to consider applications for consent for the use of such chemicals, and cannot withhold consent unreasonably. In this case, the British Government’s Veterinary Medicines Directorate has already granted a licence for Salmosan and is expected to licence Excis in the near future.

Professor David Mackay, Director of SEPA’s North Region and Chairman of its Fish Farm Advisory Group, said:

"If the Veterinary Medicines Directorate licences products, SEPA must consider applications for their use, but we will judge each case on its merits. We recognise that the salmon industry has a problem, and we will be even-handed in dealing with applications.

"However, we will grant consents to use Salmosan and Excis only under the strictest conditions to minimise environmental risk and only at sites where there are adequate water currents to disperse them quickly and safely. For instance, treatments will only take place within an enclosed tarpaulin and the salmon cages will have to be shallowed to approximately 3 metres depth. Fish farmers will be required to adopt Best Environmental Practices to minimise their use, and the quantities which can be used by a salmon farm at one time will be determined by SEPA using local water current and diffusion information.

"We will also undertake post-authorisation monitoring at fish farms to clarify the fate of the chemicals in the marine environment".

• Excis and Salmosan are both bath treatments (ie the fish are immersed in the chemicals) which kill sea-lice and other invertebrates by acting on their nervous systems.

• SEPA will consider applications for the use of the chemicals on a case-by-case basis. SEPA will only authorise the use of Excis and Salmosan for a trial period of two years while further field trials are carried out.

• Excis is designed to break down immediately after the one-hour treatment period. Trials have shown Excis does not accumulate in fish and the withdrawal period before harvesting is likely to be 24 hours. Extensive field studies in Scotland, Canada and the USA have not shown any bad effects on non-target animals (eg lobsters, mussels). Excis has a very high toxicity to crustacea in laboratory tests. However, trials with crustacea deployed around fish cages have not shown toxic effects except those located within the treated cages. This difference can be explained by the rapid break-down of the base chemical cypermethrin, allowing it to bind to particles in the water. This further reduces its toxicity. SEPA’s permission for use will be dependent on there being a rapid reduction in the toxicity to safe levels within 3 hours of release.

• Another chemical, the organophosphate Dichlorvos (product name Aquagard), has been the salmon growers’ preferred treatment for the past two decades. Its effectiveness is declining partly due to pressure from SEPA and partly because sea-lice are gaining resistance to it. Dichlorvos is a bath treatment and is a substance 'red listed' by the North Sea Conference. Salmosan, manufactured by the makers of Aquagard, has been developed to take its place. It is approximately 10 times more toxic than Aquagard but treatment involves only a tenth of the quantity of Aquagard presently used. There are already signs that sea-lice may go on to develop a similar resistance to Salmosan as they have for Aquagard.

• All except 15 of Scotland’s 415 salmon farms are prevented from using another animal medicine, Ivermectin, because of the strict limitations imposed by SEPA on its use. Consumer pressure has also led to some supermarket chains refusing to accept any salmon that have been treated with Ivermectin, which is administered in food pellets.

Under the Environment Act 1995 Section 32 (d) SEPA ‘must have regard to the social and economic needs of any area …of Scotland and, in particular, to such needs of rural areas.’ Under Section 39 of the same act SEPA must consider the costs and benefits of its decisions.

SEPA’s Fish Farm Advisory Group recently published a paper Marine Cage Fish Farming in Scotland (Regulation and Monitoring) which is currently out for consultation. The paper encourages a considered debate on all aspects of then fish farm industry, including the use of chemical treatments. SEPA will take account of the representations it receives in formulating its future policy.