Food web structure and the strength of trophic interactions in the Western Gulf of Maine Closure Area

No abstracts are to be cited without prior reference to the author.

Recent studies indicate that the establishment of Marine Protected Areas (MPAs) can rapidly influence local populations of large, predatory fish. There is far less theoretical and empirical understanding of how local increases in the size and abundance of these predators may influence food web structure and trophic dynamics within a reserve. Basic questions, such as whether the demographics of groundfish prey populations alter inside protected areas in response to predator changes, have rarely been addressed. The Western Gulf of Maine Closure Area (WGoMCA) in the northwest Atlantic, the largest MPA in the United States, has been closed to commercial bottom trawling and gillnetting for groundfish (e.g. cod, haddock, pollock, hake, flounder) since 1997. We conducted paired comparisons of contiguous open and closed fishing grounds to assess the effects of a fishery closure on the structure of the epibenthic invertebrate community. Specifically, we measured invertebrate recruitment and community development on hard substrates using heavily weighted settling platforms and quantified predation strength on prey species (e.g. brittle stars, urchins, crabs) using benthic prey tethering trials inside and outside of the reserve. Differences in recruitment inputs in both areas have shown no significant difference to date, however adult prey populations, especially crabs, exhibited elevated mortality inside the reserve. These data will be supplemented with spatially explicit stable isotope analyses to examine potential differences in predatory fish diet as a function of reserve status. Information gained from our tests inform future population and trophic modeling of the long-term impact of groundfish reserves and provide a baseline for benthic habitat productivity when fishing mortality is removed.