Trends and Potential Drivers of Distribution Overlap of River Herring and Commercially Exploited Pelagic Marine Fishes on the Northeast U.S. Continental Shelf

<p>Concern has been increasing over the impacts of incidental catches of river herring (Alewife <i>Alosa pseudoharengus</i> and Blueback Herring <i>A. aestivalis</i>) in commercial fisheries for Atlantic Herring <i>Clupea harengus</i> and Atlantic Mackerel <i>Scomber scombrus</i>, but historical information on mixed-species catches and their driving factors is lacking. We examined data from spring and fall bottom trawl surveys (National Oceanic and Atmospheric Administration, Northeast Fisheries Science Center) for temporal trends in overlap and potential ecosystem drivers of overlap trends. Species overlap changed substantially over time, with changes varying by season and region of the northeastern U.S. continental shelf. In the fall, changes in overlap were positively related to abundance in Georges Bank and southern New England. In the spring, most changes in species overlap were positively related to increasing species abundances. Positive relationships between overlap and abundance suggested that as species distributions increased with abundance, distributional overlap with other species increased as well. During the fall, changes in species overlap were positively related to bottom temperature in the Gulf of Maine, whereas in the spring, the relationship with bottom temperature was less consistent. Temperature-related changes in overlap implied that species distributions changed at different rates in response to climatic changes, thus leading to changes in overlap. Our findings suggest that fisheries management should take an adaptive approach to managing incidental catches by using region- and season-specific policies and should incorporate the effects of species abundances and climate change on species interactions.</p> <p>Received September 28, 2015; accepted October 11, 2016</p