Ecotrophic

Ecotrophic, in ecological usage, primarily refers to ecotrophic efficiency (EE) within ecosystem energy-budget models, notably the Ecopath with Ecosim framework. The term describes the fraction of production of a trophic group that leaves that group to be used by other groups or exported from the system, rather than remaining within the group as biomass or being lost to respiration or other internal processes. In practical terms, EE_i is conceptualized as the portion of production of group i that is allocated to flows to higher trophic levels or to export.

In modeling terms, EE_i is often expressed as the ratio of the sum of energy flows from group i to other groups (predation on i by predators and, in some formulations, export) to the production of group i (P_i). The flows F_ij represent the energy transfer from i to predator group j, and Exports_i accounts for material leaving the system via harvesting or other export pathways. Thus, EE_i = (sum_j F_ij + Exports_i) / P_i.

Interpretation of EE values is straightforward: values range from 0 to 1. A high EE means most of a group’s production is transferred onward to predators or removed from the system, while a low EE indicates that a larger share of production remains within the group for respiration or other non-transfer losses. EE is a parameter estimated during model construction, constrained by available production, consumption, and transfer data, and it interacts with other model components such as biomass, growth rates, and diet composition.

Limitations include reliance on data quality, assumptions of steady-state or quasi-steady-state conditions, and the simplifications inherent in aggregating species into functional groups.