Schellekens & Witbaard 2012. DEBEnsis vs. Data.

Along the Dutch coast (North sea) large quantities of sand are mined in certain locations to supply sand for coastal defence at other locations in order to retain the existing coastline. Without these nourishments of sand the coast would erode and eventually this erosion would lead to an increased risk of flooding. This project provides the unique opportunity to use measured environmental data to predict growth of Ensis directus using the DEBEnsis model and compare it to measured biotic data on Ensis. Here we report on the findings of the comparison of field data and model estimates and suggest improvements, both in field measurements, experiments and (adjustments to DEB) modelling. We state that the fit of the DEBEnsis model is adequate and use of DEBEnsis for predictive purposes on the effect of environmental changes in silt, temperature and chlorophyll are justified with this study, even though growth may be overestimated and effects of sand mining on growth and condition underestimated. Considering the overestimation of growth, to improve the fit efforts should go in determining the quantitative effects of winter- and daily feeding activity and intraspecific competition on growth.