Development and Application of Biomarker/bioassay Proceduresfor the Environmental Monitoring of Sea Lice Treatment Chemicals Used in Salmon Farming - Phase 1 Scoping Study

Sea lice (Lepeophtheirus salmonis KrÆyer and Caligus elongatus Nordmann) are ectoparasitic on salmon and browse on the skin of the fish resulting in lesions. The fish suffer from stress and increased susceptibility to secondary infections as a result of the sea lice infestations. In extreme infestations fish can suffer from osmoregulatory failure and death. The most immediate treatment for the relief of sea lice infestations on salmon in fish farms is the use of chemotherapeutants, either in baths or by oral administration in feed.

The fate of chemotherapeutants in the environment after treatment is important for the health of the marine environment around fish farms. Research is therefore required to address appropriate methods for monitoring the effects of these chemotherapeutants. Although funded by SNIFFER (the Scotland and Northern Ireland forum for Environmental Research), due to the large number of marine fish farms in Scotland relative to Northern Ireland, this study focuses on the Scottish situation. However, the techniques will have a wider applicability.

The Scottish Environment Protection Agency (SEPA) is responsible for monitoring and protecting the quality of Scottish coastal waters and, in meeting this responsibility, has a requirement to monitor the effect on the marine environment of the chemotherapeutants used in fish farms. At present SEPA undertakes routine analysis of water quality, sediment chemistry, contaminant residues in mussels and benthic community studies in relation to discharges from fish farms. Biological effects measurements which can separate the effects of the chemotherapeutants from the organic enrichment at fish farms and provide an early warning of effects, will enhance the ability of SEPA to diagnose and predict effects on the marine environment. The present study is the first part of a four phase project assessing the suitability of biological effects techniques, other than benthic community studies, for monitoring the effects of the chemotherapeutants. The aim of this phase of the study was to investigate and advise on biological effects techniques, which may be suitable to assess the biological impact of chemotherapeutants used to treat infestations of sea lice on fish farms in Scotland.

A review was carried out into which of the large number of possible biological effects techniques published in the literature are currently in use for the monitoring of marine pollution. The techniques specific to contaminants or contaminant groups, and most frequently used by the laboratories contacted were the formation of bulky DNA adducts, AChE inhibition, imposex and P450 1A enzymes. Of the non-specific techniques, the whole sediment and water bioassays, the traditional benthic community analysis, the sediment pore water and elutriate tests and the scope for growth measurement were reported to be in use in routine monitoring programmes by three or more of the laboratories.

Five groups of chemotherapeutants (two organophosphates, hydrogen peroxide, a synthetic pyrethroid, two avermectins and two benzoylphenyl ureas) are either in use or proposed for the treatment of sea lice infestations on salmon in Scottish fish farms. The specificity and suitability of the biological effects techniques to the mode of action, metabolism and fate of the chemotherapeutants were assessed. The techniques suitable for monitoring the effects of these five types of compounds in relation to the fish farm situation were selected and their status for monitoring assessed. A preliminary design and estimate of the cost of a project to investigate the dose-response relationship of the techniques, their natural variability and validation in the field was produced.

 Keywords: Biomarker, Bioassay, Sea Lice Treatment, Fish Farming

 Copies of the report are available from FWR, price £15, less 20% to FWR Members.