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(438) The ecological effects of sea lice treatment agents in Scottish sea lochs. Willis, Kate1, Black, Kenneth2, Cromey, Chris2, Gillibrand, Phillip3, MacDonald, Elspeth3, Nickell, Thom2, Pearson, Thomas4, Powell, Harry4, Somerfield, Paul5, Tarling, Geraint1, 1 2 3 4 5 ABSTRACT- Sea lice (Copepoda: Caligidae) are ecto-parasites of salmonids and severe infestations can devastate farmed Atlantic salmon. Salmon farmers generally control sea lice infestations using chemicals. Past chemotherapeutants have had relatively poor efficacy and in some cases sea lice have developed resistance. A number of new treatments are now being used world wide and much effort has gone into ensuring that these meet environmental regulatory standards. However, concerns have been raised that while these new products may be determined by standard laboratory bioassays to be safe, they could still pose an ecosystem threat. A multidisciplinary project to study potential long-term ecosystem responses attributable to these new chemicals was implemented in 1999 at three salmon farms on the west coast of Scotland. These sites currently use bath treatments of cypermethrin as the main medicine for sea lice control. By 2001, it is anticipated that these farms will also have access to in-feed treatments of teflubenzuron, diflubenzuron and emamectin benzoate. The program involves examination of littoral and sub-littoral settlement panels to assess flora and fauna settlement; sediment sampling for meiofauna, macrofauna and treatment chemicals; zooplankton sampling before, during and after medications and as a time series to assess natural variability; regular assessment of phytoplankton populations and nutrient concentrations; and hydrographic measurements to determine current flows at each site so that chemical dispersion patterns can be modelled. Given that this is a long-term project designed to study ecosystem effects rather than the acute species-specific approach of bioassays, the results to date are preliminary. Key words: ecosystem responses, salmon farming, sea lice treatments |
