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River Herring Spawning Stock Survey

Image of Blueback herring

Why this project is needed:

Recent assessments of river herring (alewife and blueback herring) stocks along the coast indicate a coast-wide decline of the stocks. In response to this, the Atlantic States Marine Fisheries Commission (ASMFC) initiated new management measures. ASMFC adopted Amendment 2 to the Interstate Fishery Management Plan (FMP) for Shad and River Herring, which all member states, including New York, must abide by. One of the management measures in this new amendment require states to provide evidence that the existing river herring fisheries are "sustainable." If the fisheries are not sustainable, then the state must shut the fishery down to all harvest.

In the spring of 2012, the DEC Hudson River Fisheries Unit (HRFU) initiated a three-year river herring spawning stock monitoring program in the Hudson River. This program is a high priority project because of the concerns over coast-wide declines of river herring and the resulting management actions adopted by ASMFC. New York must provide evidence of a sustainable river herring fishery, otherwise the state will be required to close all river herring fisheries, both commercial and recreational, in the Hudson River. The objective of this program is to gather the biological data needed to determine if river herring populations are at sustainable levels in the Hudson River. It will take several years of data collection and analysis to make a determination. More information about the management of river herring in New York State is available online.

River Herring Life History

  • Alewife arrive in the Hudson River in late March - early April when the water temperatures reach 40 degrees F, blueback herring arrive later as the water warms.
  • Alewife primarily spawn in the Hudson River and its tributaries below the Federal Dam at Troy. Bluebacks spawn in similar areas as the alewife, but have increased their use of the Mohawk River for spawning.
  • Males spawn for the first time at age 3, females at age 4. The oldest herring caught in the Hudson River was 7 years-old. In other rivers herring get as old as 14.
  • After spawning, herring return to the ocean. Some fish will return in subsequent years to spawn in the Hudson again.
Measuring a river herring in a measuring box

Survey Methods

In early spring, river herring spawn in the freshwater portion of Hudson River, including most of the tributaries. To adequately sample such a large area, we use a 300 foot haul seine. DEC field staff deploy the net with a boat and retrieve the net by hand. All captured river herring are placed into holding pens to be processed. Length, weight, sex, and spawning stage are recorded onto datasheets which are later compiled in an electronic database. A sample of scales is also taken from each individual fish to determine age. All fish are released after processing.

Next Steps

DEC staff are currently analyzing the data and scale samples collected during the 2012 sampling season and examining scale samples collected in past years. By the end of this three-year study, we will have a better understanding of the spawning stock of river herring in the Hudson River. DEC staff anticipates locating the best sites for capturing adult river herring and working with other Atlantic coast states on developing aging criteria. For more information on the river herring spawning stock survey or if you have any questions regarding the survey, please contact the Hudson River Fisheries Unit at 845-256-3172 or 845-256-3182 or at the email address in the right hand column.

Crew processing river herring on the Hudson River

Other projects

In 1999, Normandeau Associates, a contractor, started a project to monitor the spawning populations of blueback herring and alewife in the Hudson River Estuary, the Mohawk River and tributaries. The contractor collected data on size, age, sex ratio and mortality rates; and analyzed comparisons of the life history characteristics of alewife and blueback spawning populations found in each of the three areas. The contractor used many different methods to sample fish, including gill nets, cast nets, scap and dip nets, and jigging (rod and reel).

During 1999, the first year of the project, Normandeau Associates was prepared to catch and tag a large number of river herring early in the spawning run. The contractor anticipated that information gained from the return of tags by fishermen would help in the understanding of the movement of the herring throughout the Hudson River and its tributaries. During that first year over 9,000 herring were tagged. In 2000, approximately 2,400 fish were tagged and in 2001 only about 260 fish were tagged in the Mohawk River.

The report from this project is not available on-line because it is very large. If you want a copy of the report please email us (address located in right hand column).

Hudson River Estuary Program Logo

This logo represents the Hudson River Estuary Program. Click for more information about our efforts to protect this important estuary.