Alewife ( Alosa pseudoharengus ) spawning and nursery areas in a sentinel estuary: spatial and temporal patterns

Spatial and temporal distribution of anadromous alewife (Alosa pseudoharengus Wilson) spawning and nursery habitats were determined by sampling in the Mullica River – Great Bay watershed (New Jersey, USA) in a combination of long- and short-term observational and quantitative studies. Reproduction was confirmed by examination of developing gonads, visual observations of spawning, and egg collections. Spawning typically lasted 2–4 days in discrete waves in freshwater tributaries from late March to late April. Nursery habitats for larvae and young-of-the-year alewife included low-salinity tributaries near the freshwater-saltwater interface and high salinity waters through early fall before departure to the ocean in late fall. Predation on eggs by fish predators, especially American eel (Anguilla rostrata Lesueur), occurred below a dam. This predation was also observed in the laboratory on eggs and larvae. These findings point out that this dam provided for enhanced predation on alewife early life history stages, and may cause an ecological hotspot for predation-prey interactions for this anadromous species and its catadromous predator.