Exploring fish community dynamics through size-dependent trophic interactions using a spatialized individual-based model

An individual-based model named OSMOSE (Object-oriented Simulator of Marine Ecosystems Exploitation) is used to investigate the dynamics of exploited marine fish communities. It allows the representation of age- and size-stru ctured populations comprised of groups of individuals that interact within a spatialized food web. Within each group, which constitutes the basic inte raction entity (the 'super-individual' in individual-based modelling termin ology), fish belong to the same species, have similar biological parameters and behaviour rules. Somatic growth, reproduction, predation and starvatio n processes are modelled. Two rules apply for the predation process: for a given fish group, prey selection depends both on the spatial and temporal c o-occurrence of the predator and its prey, and on the respective lengths of the prey versus the predator. Thus, fish feed regardless of the taxonomy o f their prey. The strength of both predation and competition relationships therefore vary according to changes in relative species abundance. Prelimin ary investigations are conducted on a theoretical community comprising seve n interacting species. The simulation results show how community stability can emerge from variability in species biomass. It is thus suggested that s ize-based trophic interactions, along with the existence of multiple weak l inks and species redundancy, favour community persistence and stability. (C ) 2001 Ifremer/CNRS/Inra/IRD/Cemagref/Editions scientifiques et medicales E lsevier SAS.