Research Document - 2005/035

The suitability of DEPOMOD for use in the management of finfish aquaculture sites, with particular reference to Pacific Region

By Chamberlain, J., D. Stucchi, L. Lu, C. Levings

Abstract

We have applied the Scottish aquaculture waste model DEPOMOD to one British Columbia finfish farm as part of a project to test and validate this model for use in the Pacific Region. The site modeled had an extensive suite of field observations at multiple time points during a growth cycle. Detailed farm productions and configuration information were complete for the corresponding period. Since several parameter settings used in the model are not well known, we explored the effect of this uncertainty on the predicted carbon flux by running a series of simulations using a range of values representing best- to worse-case estimates. The resulting model predictions covered a broad range of outputs whose extremes represented the most optimistic and pessimistic scenarios in terms of benthic loading.

The simulation of resuspension processes within the model resulted in predictions where virtually all of the applied material was exported from the model domain and precluded meaningful comparisons of model fluxes with field data. Model predictions, with no resuspension, showed the expected steep gradient in carbon flux with distance from the edge of the net cages.

Significant relationships were demonstrated between predicted carbon flux (no resuspension) and several measures of benthic impact, namely sediment sulphide concentration, species diversity, infaunal trophic index (ITI) and faunal abundance. The sediment chemistry and biology showed a clear effect from the deposition of wastes from the finfish farm.

We discuss key limitations of the model, uncertainty surrounding model parameter settings and simulation of resuspension processes, and make several recommendations for further research and testing of the model.
 

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