Abstract

Larval fish assemblage structure, timing of ingress, and larval size were examined at Roosevelt Inlet (Delaware Bay) and Indian River Inlet (Delaware Coastal Bays) to better understand the magnitude and potential causes of recruitment variation occurring on local scales. Weekly sampling began at Roosevelt Inlet on January 30, 2006 and occurred simultaneously at the two inlets from May 15, 2006 to May 30, 2007. Univariate and multivariate biodiversity indexes were used to compare assemblage structure and seasonality between the two sites. Patterns of how estuarine spawner abundance and offshore spawner recruitment corresponded to water temperature and wind events were also shown. Whereas seasonality and species diversity were similar at the two inlets, we found significant differences in evenness due to large scale recruitment events at Roosevelt Inlet. Estuarine spawners showed similarities in timing of ingress, disappearance, and average size. Four species of estuarine spawners had peak abundances that were larger by an order of magnitude at Roosevelt Inlet. There were significant differences in offshore spawner timing of ingress and average size. At Roosevelt Inlet larvae were significantly larger (Atlantic croaker and Atlantic menhaden), and persisted longer in the collections. Results also show a correspondence between northwest winds and large scale recruitment events at Roosevelt Inlet. Indian River Inlet lacks these large scale recruitment events which may imply that viable transport mechanisms make Roosevelt Inlet more suitable for ingress of offshore spawners.