...managers should have a conceptual understanding of the food web, and should use that information in making decisions about harvest...the FEP should contain an analysis of the anticipated impacts of the allowed harvest on predator-prey dynamics, even if data gaps force such a statement to be largely qualitative.
Ecosystem Report to Congress, 1999
A balanced food web is one of the most important factors of a functional ecosystem. To gain a conceptual understanding of food web dynamics, information should be obtained on predators and prey for each functional group in the ecosystem. A functional grouping is made up of species sharing similar ecological roles, i.e. plankton-eating fishes. Food webs in the marine environment, however, are extremely complex and information on the diet of marine organisms is limited at best.
Fortunately, mathematical models exist that can assist fishery managers in characterizing the trophic structure of an ecosystem. One such model, Ecopath with Ecosim, has been used extensively to examine the dynamics of aquatic food webs.
An Ecopath model is a snapshot of the food web components of an ecosystem and their interactions, represented by linked functional groupings of a single or multiple species. The model is constructed by defining a model area and time, organizing species into functional groupings, and estimating the trophic characteristics (energy flow) among groupings. Ecopath models are then "balanced" in terms of mass or energy to obtain a whole-system view of the biological community.
A preliminary South Atlantic Bight Ecopath model was developed cooperatively as part of the Sea Around Us project funded through the PEW Charitable Trust Foundation. This model is being refined with the aid of a broad range of experts to be incorporated into the Council's Fishery Ecosystem Plan. Thus, it will help the Council and other decision makers identify information gaps and direct future research while providing insight into ecosystem level effects of fisheries. The model will cover the area between North Carolina/Virginia border through the Florida Keys and will extend from the upper wetlands to the 300-meter depth contour.