River Herring Conservation

Throughout much of recent history, river herring were abundant along the Atlantic coast. However, River herring are in trouble. This project studies two species (alewife, Alosa pseudoharengus and blueback herring, Alosa aestivalis). These fish are anadromous, just like salmon, which means that they mostly live in the ocean, but travel to freshwater streams to reproduce, or spawn. Because populations have declined over the last few decades, several river herring fisheries (including the ones Chesapeake Bay) have closed. River herring are important prey for herons, eagles, ospreys, striped bass, and many other bay species. The Chesapeake Bay River Herring Project, led by SERC’s Fish and Invertebrate Ecology Lab, hopes to track herring Chesapeake Bay tributaries to identify how many river herring there are and identify any changes in their populations.

An important part in restoring river herring is understanding where they are spawning, so that fisheries managers can focus on protecting those habitats. Right now, we want to know:

Learn more about the River Herring Conservation Project here!

Want to get involved? 

Volunteers are involved in both the field and lab activities of the Chesapeake Bay River Herring Project. Click here for more information about how to sign up.

The "What" and the "Why"

What are we trying to learn?

We want to know where river herring are traveling to spawn. Herring spend most of their lives in saltwater but travel to freshwater to spawn. By identifying where herring spawn we can identify ways to encourage spawning. Humans have restricted herring access to traditional spawning areas through dams and destruction of habitats. Some dams have fish ladders, which is a series of steps and pools built next to dams that allow fish to bypass the dam and get to waters on the other side. Unfortunately many fish ladders have been found to be ineffective due to their location (the ladder will begin too far from the dam, and is not conducive to herring behavior). In Maryland, a number of dams are being removed out of concern for public safety as well as the effects on herring and shad (another species that travels upstream to spawn). SERC researchers want to know how and if the removal of these dams will have an effect on herring movement throughout tributaries. 

Why do we care about River Herring? So what if they disappear? 

There are really big ecological and economic consequences to losing river herring! Historically, river herring have been one of the most abundant fish in the Chesapeake Bay. Many larger birds and fish rely on herring as a food source. If herring disappear entirely, their larger predators such as striped bass, blue herons, and osprey also become at risk. Humans have also contributed to the decline of river herring population. Dam construction restricts herring spawning migrations, and increased fishing pressure throughout the latter half of the 1900’s drove down herring population. Additionally, the decline and destruction of spawning habitats restricts where herring are able to spawn.

River Herring are already under a moratorium along most of the east coast. This means people can’t intentionally catch herring, or have herring in their possession. The only river sustainable herring fisheries that remain open are in Maine, New York, New Hampshire, Rhode Island, North Carolina, and South Carolina.


Volunteers who work with this project can be involved in both the field and the lab activities.

In the field…

Dave measuring fish

We sample once a year, in the spring. The two species of river herring make their spawning runs up the rivers at different times. Alewife spawn in March and early April, and blueback herring during late April and early May. We can plan for herring runs, and target sampling time at the peaks, so we get the best representation of actual populations. We have a number of sites throughout the Bay area and we arrange teams to go out to the sites to collect data. Training and equipment are provided.

When we get to the sites, we collect information about the stream location (temperature, how fast the water is flowing) and determine whether river herring are present or absent. We do this visually, and by collecting samples that will later be processed in the lab.

In the lab…

One of the sample types collected at each site is meant to check for herring eggs and larvae. These samples are processed back in the lab at SERC under a microscope.

We also want to know how many river herring there are at a particular location, but since the water is often murky, we use a sonar system called the Dual-frequency Identification Sonar (DIDSON) in order to see fish in the water. The DIDSON collects footage of the fish that swim by it, and scientists use this footage in the lab to count all of the river herring that swim by that sonar station. Unlike a regular waterproof camera, the DIDSON is able to see through murky water, and unlike people, the DIDSON can stay out in the water for weeks at a time! After the footage has been collected, it is analyzed in the lab to determine a total count of river herring for a tributary estimates about the size of the fish. With some training, volunteers can help us with this footage analysis.

Get Involved

We ask that volunteers be able to join us for one full day in the field (as a one time commitment). If you are interested in working in the lab, we ask that you come in at least one half day per week, over 3 months.

All participants must be 16 and over, because the project involves lab work.

Location and Days/Times

Field sampling days vary from year to year depending on when the fish are spawning, but generally occur between March 1 and May 31.

Most volunteers meet us at the SERC campus in Edgewater, MD and travel with researchers to the sites. Because of permitting restrictions, a member of the SERC staff must be present at all data collections. In the future, we hope to find ways for individuals to go out on their own to sample at sites convenient to them.

There are opportunities in the lab for volunteers who want to sort through egg and larvae samples using microscopes or help analyze DIDSON images and videos. The timing of these opportunities is flexible.

To sign up or for more information

Contact Alison Cawood, SERC Citizen Science Coordinator, at cawooda@si.edu, 443-482-2271.