Advancing an Ecosystem Approach in the Gulf of Maine

Abstract

<i>Abstract</i>.—The northeast U.S. Continental Shelf large marine ecosystem (NES LME) has supported important commercial fisheries for several centuries. The NES LME has experienced structural change due to both intensive exploitation and physical forcing in relation to broader climate impacts in the North Atlantic over the past several decades. Here, we examine the combined effects of anthropogenic and environmental factors on the state of the NES LME using a driverpressure- state-impact-response framework to structure our assessment of patterns of change in this system. We partitioned both drivers and pressures according to natural and anthropogenic sources. Ecological state variables encompassed a broad spectrum of trophic levels. Impact metrics are based on economic trends in the fisheries. To represent regulatory responses, we trace the history of management actions in this region over the past five decades. The critical importance of changes in temperature and water column stratification in ecosystem change, in relation to bottom-up forcing, is identified using canonical proredundancy analysis. Analysis of anthropogenic pressures indicate a clear effect of fishing pressure, and removals due to fishing, in the dynamics of fish communities in the region, highlighting an important top-down control mechanism. Analysis of zooplankton community dynamics confirms previous indications of a regime-like change in species composition during the 1990s. Observed changes in fish community dynamics appears to be most clearly related to large-scale switches from a demersal to a pelagic fish dominated system and to changes within the demersal fish community itself.