Species-Specific Differences in the Diets of Forage Fishes on the NE US Continental Shelf

Small pelagic fishes (i.e. ‘forage fish’), as intermediate consumers, are an important link between plankton and upper trophic levels. Yet this link is generally poorly understood, and notably so on the Northeast US continental shelf. In this region, populations of small pelagic fishes are known to fluctuate widely in time and space, which leads to variability in consumption by predators as well as in top-down effects on zooplankton. To investigate the trophic role of small pelagic fishes, Atlantic herring, alewife, blueback herring, Atlantic mackerel, butterfish, and sand lance were collected from NOAA’s NEFSC spring and fall bottom trawl surveys in 2013 and 2014. Thorough, lab-based visual inspections of the gut contents of these fish were conducted, identifying all prey to the lowest taxonomic level possible. Preliminary analyses of mackerel and Atlantic herring diets have revealed spatial and temporal differences between species, in addition to evidence of high reliance upon appendicularians and, for mackerel, larval fish. When combined with ongoing work on compound-specific and bulk stable isotope analyses, results of this study will greatly enhance our knowledge of the trophodynamics of small pelagic fishes and their ecological role within the Northeast Shelf Large Marine Ecosystem.