Effect of Striped Bass Larvae Transported from the Hudson River on Juvenile Abundance in Western Long Island Sound

Freshwater flow can have a profound influence on the transport of larvae within large tidal estuaries, and tidal flow can transport larvae away from those estuaries. Our objectives were to (1) confirm that a combination of freshwater and tidal flows transported post-yolk-sac larvae (PYSL) striped bass Morone saxatilis from the Hudson River, New York, to western Long Island Sound (WLIS), a nearby nursery area, and (2) assess the effect of PYSL transported from the river on the abundance of juvenile striped bass in WLIS. This approach included (1) calculating an index of juvenile striped bass abundance in WLIS (WLIS juvenile index) for July and regressing it on an index of striped bass PYSL abundance for the Battery region of the Hudson River (Battery region PYSL index), which represented annual changes in the abundance of striped bass PYSL that could be transported from the river to WLIS, and (2) regressing a WLIS juvenile index for August on the WLIS juvenile index for July. The regression of the WLIS juvenile index for July on the Battery region PYSL index was significant and positive. The regression of the WLIS juvenile index for August on that for July was not significant. We confirmed that striped bass PYSL were transported from the Hudson River to WLIS by a combination of freshwater and tidal flows. Furthermore, in years when striped bass PYSL abundance and freshwater flow in the Hudson River were unusually high, striped bass PYSL transported from the Hudson River substantially influenced abundance of juvenile striped bass in WLIS during July but not August. The difference in abundance between months was apparently due to high natural mortality early in the juvenile life stage.