Predicting the impact of marine cage fish farming on the seabed: DEPOMOD Kenneth D Black1, Trevor Carpenter1, Steve Gontarek1, Kevin Black2, Saul Reynolds2, Carl Amos3 1. SAMS, Scottish Marine Institute, Oban 2. Partrac ltd, Glasgow 3. Tuscan Consultancy Ltd., Landford Fish-farms discharge waste (fish faeces, food waste and chemical treatments) which can accumulate on the seabed causing organic enrichment which can lead to conditions toxic to marine life. AutoDEPOMOD is a model for predicting the impact of fish-farm discharges on the seabed in order to optimise the operation of aquaculture sites to match the environmental capacity. AutoDEPOMOD (originally co-funded by NERC in 1998) uses site specific conditions such as current speed, water depth, fish biomass and feed volume to predict discharge amount and deposition area. In 2001, SEPA supported further development of the model to examine the discharge of sea-lice medicines from fishfarm sites in order to derive appropriate limiting license conditions for discharge. In 2005, AUTODEPOMOD was adopted by SEPA as a compulsory step in the planning process for new and expanding aquaculture sites. The model is also licenced in ~25 other countries with Mediterranean and Philippine variants funded through EU projects. Scottish Government have funded a major project to re-parameterize and recode AutoDEPOMOD to allow it to better simulate sediment resuspension processes (see below), accept spatially varying currents from hydrodynamical model outputs, providing improved code and architecture that can efficiently utilise modern computing options (PC to cluster). Building on this, BBSRC/NERC are funding new research to develop a biogeochemical module to allow prediction of sulphide concentrations and oxygen demand. Example sediment concentration (turbidity) time series showing the various phases of an erosion experiment. Deploying the Voyager II benthic flume from SEPA’s Sir John Murray SAMS, Scottish Marine Institute, Oban, Argyll, PA37 1QA T: (+44) (0)1631 559000 F: (+44) (0)1631 559001 E: info@sams.ac.uk W: http://www.sams.ac.uk Cromey, C.J., Nickell, T.D. and Black, K.D. 2002. DEPOMOD - modelling the deposition and biological effects of waste solids from marine cage farms. Aquaculture. 214. 211-239. Cromey, C.J., Nickell, T.D., Black, K.D., Provost, P.G. and Griffiths, C.R. 2002. Validation of a fish farm waste resuspension model by use of a particulate tracer discharged from a point source in a coastal environment. Estuaries. 25. 916-929. Cromey, C.J., Nickell, T.D., Treasurer, J., Black, K.D. and Inall, M. 2009. Modelling the impact of cod (Gadus morhua L) farming in the marine environment-CODMOD. Aquaculture. 289. 4253. Cromey, C.J., Thetmeyer, H., Lampadariou, N., Black, K.D., Kögeler, J. and Karakassis, I. 2012. MERAMOD - predicting the deposition and benthic impact of aquaculture in the Eastern Mediterranean. Aquaculture Environment Interactions. 2. 157-176. Keeley, N.B., Cromey, C.J., Goodwin, E.O., Gibbs, M.T. and Macleod, C.M. 2013. Predictive depositional modelling (DEPOMOD) of the interactive effect of current flow and resuspension on ecological impacts beneath salmon farms. Aquaculture Environment Interactions. 3. 275-291. Acknowledgments Scottish Government; SEPA; the crews of Sir John Murray, Calanus and Seol Mara; Scottish Seafarms, Marine Harvest; Scottish Salmon Company, Kames Fish Farming ltd.