MYSTIC RIVER HERRING RUN 2023: ~470,000
According to the official estimate from the Division of Marine Fisheries (Mass DMF), around 470,000 river herring passed through the fish ladder at the Mystic Lakes Dam in Medford in 2023 and around 12,000 herring made it into Horn Pond. This number represents a strong and stable population of river herring migrating through the Mystic River in 2023 amid fluctuations across the state. The next frontier for the expansion of the herring population is Horn Pond, a large body of water in Woburn, where a dam prevents many fish from accessing additional spawning habitat. Plans are underway to build fish passage at Horn Pond, using federal and local funding.
About River Herring
River herring — Alewife and Blueback herring — are migratory species that spend most of their lives in the open ocean, but return to freshwater every year to spawn in the river system they were born in. Herring have long been an important resource for native people in this area. They also have a crucial role in freshwater and marine food webs. They are prey for seals, and other marine mammals in the ocean; seabirds, cormorants, ospreys, herons, and eagles; tuna, cod, trout, and several species of bass; mink, fox, raccoon, skunk, weasel and turtles. As zooplankton eaters, they turn an inaccessible resource into the food for a large number of species humans consume, enjoy and profit from.
Herring are threatened by overharvesting in the ocean and — crucially — by the loss of inland habitat for breeding caused by dams blocking access to inland lakes and streams. The recent count represents the continuation of an urban ecological restoration success story that has included the installation of multiple fish passages on the river resulting in a sharply rebounding population of river herring in the Mystic River. The opening of a new fish passage at Horn Pond would present the next big opportunity to boost the Mystic’s herring run.
HERRING NUMBERS IN CONTEXT
This year’s estimate is slightly higher than last year’s and consistent with the sense that the Mystic population remains robust. (Fish populations fluctuate over time for multiple reasons). Despite running through a dense and highly urbanized environment, the Mystic is today usually among the largest documented herring runs in the state. This year it was the second largest after the (aptly named) Herring River in Wellfleet — a protected estuary on Cape Cod Bay.
Across Massachusetts, herring populations on average showed some recovery following an abnormally low year in 2022. In 65% of individual runs across the state, the population of herring grew. Despite the statewide fluctuations, the Mystic’s population has remained fairly steady since 2015. “This year's counts at Mystic Lake and Horn Pond show the continued strength of the Mystic River herring migration, one of the largest in the Commonwealth,” says John Kilborn, a long-time volunteer herring monitor and herring advocate. “The migration success is a positive sign for the new fish passage to be built in Horn Pond in Woburn. That passage will open up new lake habitat that will help the threatened herring rebound even more.”
The last time the Mystic River saw a dramatic increase in the herring population was the result of the construction of the fish ladder at the Mystic Lakes Dam in Medford. Horn Pond remains the next and last major water body in the Mystic River watershed that could offer new spawning habitat to herring, sustaining a larger total population.
HoRN POND AND THE SCALLEY DAM
The success of the Mystic River’s herring migration has been due in large part to the participation of resident volunteers, who have made the Mystic’s herring run one of the best attended, most reliable herring counts in the state.
“Citizen scientists make many contributions to the monitoring, management and restoration of natural resources,” says John Sheppard of the Massachusetts Division of Marine Fisheries. “They are the eyes and ears on the water for managers and have collectively helped create one of the most extensive state monitoring networks for river herring. The effort to monitor the river herring run at the Mystic River has indicated it is one of the largest in the Commonwealth. Monitoring has documented the success of fish passage improvements at the Mystic Lakes and highlighted the potential to expand the population by accessing additional habitat within the watershed.”
Since 2012, the herring population in the Mystic has more than doubled, due to the construction of fish passages at the Mystic Lakes Dam and the Center Falls Dam, which introduced more than 200 acres of habitat for herring to spawn.
Volunteers have also monitored fish entering Horn Pond, where the Scalley Dam blocks passage into the last big body of water in the watershed. This year, only around 12,000 fish made it into the pond via a small cascading stream that goes around the dam when the water levels are high enough. However, for every fish that made it into the pond, hundreds more congregated at the base of the dam, most of which presumably turned back downstream.
Image: The Scalley Dam and spillway at Horn Pond in Woburn, MA - Credit, Sarah Bergman-McCool
Following two federal environmental damages settlements — including the famous Superfund cases in Woburn — millions of dollars of investment will be brought into constructing a new fish ladder at Horn Pond, which will open up more than a hundred additional acres of spawning habitat. The City of Woburn is also investing in this project, which has entered its permitting phase. Upon the completion of this project, herring in the Mystic River watershed will have access to much of their ancestral range.
In addition to new habitat for herring, the project aims to include an accessible viewing platform and a viewing window that will allow visitors to see the migration from above and below the water, giving residents first-hand experience of an ecological marvel in their own backyard.
With this exciting expansion on the horizon, it is possible that the Mystic could one day boast a million-herring run. We are incredibly thankful to the team of volunteers who have made all of this progress possible.
River Herring swimming upstream in the spillway at Horn Pond - Credit, Daria Clark and Jennifer Delgado
get involved
Will the Mystic herring run reach a million fish? Will the Mystic continue to lead the state in herring populations? Stay tuned for more data from a remarkable urban wildlife migration and, keep an eye out for volunteer opportunities to participate in our in-person and video counting programs. Registration to be a herring monitor for the 2024 season will open in February/March.
In the meantime, you can learn more about current opportunities to explore the Mystic at our website.
