Foraging Potential of Larval Alosines in the Lower Roanoke River and Albemarle Sound, North Carolina

Zooplankton composition and abundances were quantified in the lower Roanoke River and Albemarle Sound, North Carolina. The spatial and temporal overlap between larval alosines, including American shad Alosa sapidissima, river herring (alewife A. pseudoharengus and blueback herring A. aestivalis), hickory shad A. mediocris, and zooplankton were examined to determine whether larval alosines in this system are food limited. Samples were collected weekly at 19 stations from March through June 2008-2009 in three habitats: River, Delta, and Sound. Spatial differences in zooplankton were observed, with the abundance in the Sound (16,546 +/- 14,678 [number/m(3) +/- SD]) being significantly higher than those in the River (4,934 +/- 3,806) and Delta areas (4,647 +/- 2,846). Zooplankton composition was dominated by Daphniidae, Bosminidae, calanoid and cyclopoid copepods, copepod nauplii, and rotifers. The spatial patterns in alosine abundance were the opposite of those for zooplankton, being highest in the River (21.0 +/- 127.6) and lower in the Delta (7.5 +/- 35.5) and Sound (4.6 +/- 24.8). Mouth gapemodels for each alosine species showed that copepod nauplii and rotifers are the most suitable-sized prey for the first feeding after yolk sac absorption. There was a high degree of spatial and temporal overlap between larval alosines and size-appropriate prey items, suggesting that the larval alosines are not food limited in Albemarle Sound.