Critical points in ecosystem responses to fishing and environmental pressures

Ecosystem dynamics are often influenced by both environmental and anthropogenic pressures. Increased demand for living marine resources has resulted in global declines of targeted species, which are often managed under a single-species paradigm that does not fully incorporate ecosystem considerations such as ecological interactions or environmental factors. Ecosystem-based fisheries management (EBFM) is a more holistic approach that concurrently addresses human, ecological, and environmental factors influencing living marine resources and evaluates these considerations collectively on a system level. For EBFM, reference points associated with management action need to be quantified. Methods have been developed to assign decision criteria to ecological indicators' response to human-use pressures, yet few efforts have established decision criteria in response to the combined influence of human-use and environmental pressures. We translated ecological indicator response into a surface dependent on both fishing and environmental pressures. Using generalized additive models, we empirically determined critical points at which a small change in fishing and environmental pressure results in an abrupt change in ecosystem status. For the Northeast United States Shelf Large Marine Ecosystem, we identified critical points in ecological indicators that represent system production, size distribution, community structure, and ecosystem functioning. Our findings highlight the need to include both anthropogenic and environmental pressures for delineation of ecosystem decision criteria.