Striped Bass Predation Drives River Herring Population Dynamics

Striped bass (Morone saxatilis) are large anadromous serranids that ascend rivers in the spring on spawning and feeding migrations, simultaneously with spawning migrations of anadromous Alosa species, including river herring. Several diet studies found that the preferred prey of striped bass are members of the Clupeidae, including the genus Alosa. Consequently, because the science of ecology has found that primary predators can affect the survival and abundance of important prey, striped bass can potentially affect or control the abundance of Alosa species. This hypothesis has been tested for the Connecticut River population of blueback herring and the Delaware River spawning stock of American shad and was not rejected. Because striped bass attained historically unprecedented abundance from 1995 through the late 2000s, the large reduction in abundance of Alosa species is consistent with the hypothesis of predatory control of Alosa abundance.  The decline in total abundance of striped bass in recent years, due to the absence of production of a dominant year class in the Chesapeake Bay from 2003 until 2011, resulted in an increase in abundance of American shad and river herring on the Atlantic coast, consistent with the hypothesis of a dominant effect of striped bass predation.