Ecosim

Ecosim is a dynamic, multi-species ecosystem model used to simulate how marine ecosystems respond over time to changes in fishing pressure, climate, and other drivers. It is a component of Ecopath with Ecosim (EwE), a framework that integrates static trophic relationships (Ecopath) with time-dynamic simulations (Ecosim) to support ecosystem-based fisheries management.

Model structure: Ecosim uses differential equations to track biomass of functional groups, accounting for production, consumption, predation, and losses. The interaction strengths are modulated by vulnerability parameters that describe how predators switch among prey. The model requires an Ecopath snapshot as input, including biomass, production/biomass, consumption, and an initial diet matrix; and it uses forcing variables like fishing effort or environmental productivity to drive dynamics.

Applications: Scientists use Ecosim to explore consequences of fishing scenarios, marine protected areas, gear changes, or climate shifts on ecosystem structure and fish yields. It provides time series outputs for biomass, catches, and trophic flows, enabling retrospective and prospective analyses.

Development and usage: Ecosim is part of the Ecopath with Ecosim software suite, widely used in research and policy discussions around ecosystem-based fisheries management. It has been applied globally across oceans and seas to examine ecosystem responses to management interventions and natural variability.