Ecopath

Ecopath is a mass-balanced, ecosystem modeling framework used to describe energy flows among functional groups in an aquatic ecosystem. It provides a static, quantitative snapshot of trophic interactions, based on observed or estimated biomass, production/biomass, and consumption/biomass ratios, together with fishing and other mortalities.

In Ecopath, the ecosystem is represented as a set of functional groups connected by flows of energy. The model solves for the flows among groups (Fij) such that production of each group is balanced by predation and other losses. Key parameters include biomass (Bi), production/biomass (P/B), consumption/biomass (Q/B), catch, and ecotrophic efficiency (EE). EE is the fraction of production that is utilized within the system (through predation and exports). The result is a mass-balanced depiction of energy transfer and trophic structure.

Ecopath provides estimates of all flows between functional groups and a diagnostic overview of the ecosystem’s energy budget. It is commonly used to assess the effects of fishing, habitat alteration, or climate-driven changes, and to inform ecosystem-based management. The approach supports the identification of key species and energy pathways, and serves as a foundation for scenario analysis.

Ecopath with Ecosim extends the static Ecopath framework by adding dynamic simulations (Ecosim) and, in some implementations, spatial dynamics (Ecospace). The Ecopath family was developed in the 1990s by researchers including Christensen and Pauly and has since become a widely used tool in marine and freshwater ecosystem assessment and fisheries management.

Limitations include dependence on data quality, the static nature of the core model, and the simplification of complex ecosystems into discrete functional groups.