Shrimp Trawling, Ecosystem Impacts, Climate Change, and the Future of Wild Shrimp Harvests: A Network Modeling Approach

Bottom trawling captures shrimp and a large number of non-target fish and invertebrate species (by-catch).  Although 11,700 trawling trips have been recorded in Core Sound in areas open to trawling since 2001, this number has recently been declining to low levels.  We used biological sampling and harvests from the North Carolina Division of Marine Fisheries to construct ECOPATH models of trawling impacts and other gears in Core Sound. We explored some of the ecosystem differences between open and closed areas using ECOPATH model outputs and predict the future of shrimp trawling using ECOSIM. We examined ECOSIM scenarios that included lower shrimp trawling, a gill net ban, and increased salinity due to climate change.   Net primary production computed in ECOPATH was greater in the open trawling areas.  Reduced shrimp trawling will produce more jellyfish, flounders, and shrimp. A gill net ban will increase the biomass of striped mullet, sharks, flounders and red drum.  Climate change will increase salinities, leading to more shrimp biomass.  ECOPATH models allow exploration of indirect impacts.