Oct 1, 2026

The NROC Tribal Caucus sought to centralize information about river herring and shad runs in New England to support scientific understanding and inform decision-making about protection and restoration of diadromous fish habitats and populations.

The new River Herring and Shad Runs layer provides point locations of fish runs throughout the Northeastern U.S. with links to additional information on managing entities and fish counts. The data were aggregated from a number of sources, including the Massachusetts Division of Marine Fisheries, the Peconic Estuary Partnership, and the ECOFish Shad and River Herring Run Data Portal (created by the Gulf of Maine River Herring Network and the Mid-Atlantic Fishery Management Council, hosted by Manomet).

To access the River Herring and Shad Runs layer, navigate to Fish > Diadromous Fish Runs.

Fish

Data Provider(s):

  • Association to Preserve Cape Cod
  • Atlantic States Marine Fisheries Commission
  • Buzzards Bay National Estuary Program
  • Connecticut River Salmon Association
  • Gulf of Maine River Herring Network
  • Maine Coast Heritage Trust
  • Maine Division of Marine Fisheries
  • Maine Rivers
  • Massachusetts Division of Marine Fisheries
  • Peconic Estuary Partnership
  • Rhode Island Department of Environmental Management
  • Save the Sound
  • U.S. Manomet Conservation Sciences
map of river herring and shad runs on the Northeast Ocean Data Explorer
Launch Interactive Map

River herring and shad, which migrate between river and ocean habitats as part of their lifecycle, are culturally, ecologically, and commercially important species with declining population numbers along the east coast. Populations have been declining for many years due to habitat loss, barriers to upstream habitat (e.g., dams, culverts) and bycatch in the Atlantic herring fishery, prompting numerous initiatives to assess river herring populations and to restore and protect their habitat. Many of these challenges are shared by other diadromous species in the Northeast U.S., though conservation and population assessment initiatives vary by species. The NROC Tribal Caucus is interested in expanding the River Herring and Shad Runs layer to include runs for other species in the future.

Fish runs are the specific migratory pathways that diadromous fish take to complete components of their lifecycle. In New England, many state governments, non-profit organizations, and community science groups conduct surveys of fish runs to document their location and/or assess fish population size. Runs for river herring and shad represent pathways that these fish take as they migrate from the open ocean to lay eggs in freshwater.

The term “river herring” refers to two species of diadromous forage fish, alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis). Shad (Alosa sapidissima) is the largest herring species in North America.

The data in the River Herring and Shad Runs layer were compiled from several existing online maps and atlases, including:

The Northeast Regional Habitat Assessment (NRHA) Data Explorer homepage. To find species abundance maps, select “Species View”.

To access these new data layers, Northeast Ocean Data Portal users can navigate to “Fish” under the Table of Contents, then select “Federal and Coastal Trawls by Species”. Select the NRHA tab, then the species and season of interest. An outline showing the extent of each trawl survey will also appear on the map with these layers, but note that the inclusion of each trawl in determining species relative abundance depends on the species and season. For more information, click on any hexbin of interest and the trawls included in the value for that hexbin will be provided under “Trawl_Sources.”

To access these new data layers, Mid-Atlantic Ocean Data Portal users can navigate to “Marine Life Library (Species Specific)” under the Table of Contents, then select “Fish BioMass NRHA Abundance” and select the species and season of interest to add to the map. There is also a layer “Coastal Trawl Extents” that will show the extent of the coastal trawls included in the NRHA data. Please note that not all trawls are included in every species or season, so to understand which trawls were used to calculate the relative abundance of any given hexbin, click on that hexbin and the field “Trawl_Sources” will identify the trawls used for that cell.

MDAT first developed coastal fish data products in 2016, reflecting the Maine/New Hampshire trawl, the Massachusetts Division of Marine Fisheries trawl, the North East Area Monitoring and Assessment Program (NEAMAP) trawl, and the Connecticut DEEP Long Island Sound trawl. These data products are now considered archived but are still available in the table of contents under Fish > “View Archived Coastal Trawl Data”.

Learn More on Webinar
Join us for a special “How Tuesday” webinar hosted by the Mid-Atlantic Data Portal team and focused on these data and the NRHA effort they were derived from on Jan. 27 at 11 a.m.

In this session, Duke University Marine Geospatial Ecology Lab (MGEL) Geospatial Analyst Sarah DeLand will provide an overview of the data, how it was compiled, and how to access them on the Mid-Atlantic and Northeast Ocean Data Portals. Mid-Atlantic Fishery Management Council Fishery Management Specialist Tori Kentner will share further background on NRHA and demonstrate how to access many additional marine life map products via the NRHA Data Explorer.

The webinar is open to the public and will include a Q&A with the presenters. Click here to register. A Zoom link will be provided upon registration.