Alewife (Alosa pseudoharengus) and Blueback Herring (Alosa aestivalis), collectively referred to as river herring, are anadromous fish living much of their life in the ocean but which migrate to freshwater to spawn in the same streams they were born in. In the Chesapeake Bay region, Alewife begin their spawning runs in late February and early March with Blueback Herring appearing in April. Historically, river herring supported a highly valuable fishery along the Atlantic Coast of North America and were an important component of coastal food webs. Over the past few decades, river herring populations have declined by more than 90% due to habitat loss, overfishing, pollution and other threats like declining water quality, alteration of physical characteristics of streams, and issues related to climate change. We work with federal, state, academic and NGO partners to document and monitor river herring spawning in the Chesapeake Bay in an effort to conserve and restore this once prosperous and important forage fish and fishery. We also hope to understand how different land uses along streams and in watersheds affect how river herring use these spawning streams.
We’re documenting the presence or absence of river herring in the major tributaries of the Chesapeake Bay, and in those tributaries where we find river herring we’re using sonar, animal tracking, and environmental DNA technology, along with traditional biological sampling, to study population dynamics. We combine these data with maps of land cover, topography, and stream networks to quantify the land uses associated with river herring presence in streams. We can examine the land near a fish survey point, the land along the stream that the herring swam up to reach the survey location, and the watershed that drains to the survey location. We use statistical models to understand how these measures relate to river herring habitat use and to predict how likely river herring are to be present in other streams.