Example ofmodel vs. observations.Model simulation assumed ρS=0.2; ρC=0.7; ρB=1;mN= 0.001;megg= 0.98. Field observationswere obtained by: a) and b) (Beukema and Dekker, 2007) on the total number of individuals in the mussel bed at the Balgzand area with size above 0.1 cm and size distribution; c) and d) (de Vooys, 1999) on the abundance of mussel larvae on the western part of the Dutch Wadden Sea, and e) Rob Dekker (unpublished data) on spat abundance of mussels at locations A and B represented in Fig. 1. Larvae correspond to an organism of size range [0.0073; 0.026] cm in the model and size higher than 0.007 cm in the field data. Individuals with size [0.03; 0.15] are considered to be spat in the model and in the observations.