Model Overview Main Assumptions

Model Overview Main Assumptions

OSMOSE is a spatial multispecies size-structured model based on opportunistic predation between a predator and its prey. This individual-based model represents the whole life cycle of several species from eggs and larvae up to juveniles and adults. This model focuses primarily on fish, but also includes elasmobranchs, cephalopods, and crustaceans. The model core element is called a “school” and represents a group of identical fish, i.e., individual fish sharing identical values for their state variables: primarily size, age, trophic level, location, species, weight but also gonadic weight, maturity state and genome structure when required.

During each time step, each school undergoes different processes: movement, interactions with the environment and other schools, growth and reproduction.

Predation results from interactions with the environment (plankton and benthic prey) and other schools. It occurs when there is spatiotemporal co-occurrence and a size match between a predator and its prey. Consequently, the structure of the food web is not static but results from local trophic interactions among schools.

There is a wide variety of options for representing fishing pressure: from a simple species-specific fishing mortality rate (F) to an explicit fleet structure that varies in space and time.