Department of Environmental Conservation

D E C banner

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. . In 2014, the project was extended additional two years, running through 2016, to ensure adequate data collection in order to develop an appropriate management strategy. 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 9 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 have analyzed scale data from 2012-2013 and are currently analyzing data from scale samples collected during the 2014 sampling season as well as examining scale samples collected in past years. By the end of 2016, we will have a better understanding of the spawning stock of river herring in the Hudson River. In 2014, DEC staff completed a river herring spawning stock survey progress report to the New York Ocean and Great Lakes Ecosystem Conservation Council outlining project objectives and reporting on data collected in 2012 and 2013.
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 845-256-3171 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-stream fish counter

In 2013 and 2014, we conducted a pilot study using an in-stream fish counter in Black Creek, (located just south of Kinston NY), a small tributary with a known river herring spawning run. The primary objective was to determine if a fish counting device was an appropriate method to collect absolute abundance data for river herring in small tributaries. Our secondary objectives were to identify when river herring migrate into tributaries and to identify parameters that may influence those migrations (i.e. moon phase, water level, water temperatures).

River herring counter in Black Creek, Hudson River tributary.

The study design consisted of a stream wide weir to guide river herring through a counting device and a Smith Root SR-1601® multichannel fish counter. NYSDEC staff built the counting head using four inch PVC tubes stacked in two rows of four, forcing fish throughone of eight individual counting tubes. We installed the counter system at the end of March in both 2013 and 2104, close to the head of tide, and it remained in place until the end of May in both years. Staff attempted to visit the counter on a daily basis. During site visits, technicians recorded fish counts on the counter system, along with any applicable environmental observations, such as weather conditions, temperature, and water level. Once the daily count was recorded, the counter was reset to zero. We also conducted multiple visits during the same day on several different occasions in order to record day versus night timing of river herring movements into the tributary. We also incorporated a trap into the design of the weir in 2013, attached to the counter exit directly up stream of the weir to determine species composition of the fish going through the counter. The trap was closed on five occasions at various times throughout the run. We then attempted to use these trapping results as a correction factor to the final count data; however, it was very difficult to capture every fish in the trap due to the stream substrate as well as impaired visibility. At this time we do not have an accurate correction factor. To address this, we installed a video camera system in 2014 to verify counts and create an accurate correction factor. The 2014 video data is currently being analyzed.


In 2013 and 2014, we observed 205,426 and 578,073 counts respectively. Note that these numbers are raw data and need to be adjusted for the previously mentioned issues i.e. double counting, presence of non-target species. There appears to be a bimodal spawning pattern in 2014, which is supported by previous studies (Lake & Schmidt 1997 & 1998; Schmidt & Tillman 1994). Peaks in migration into Black Creek appear to correlated to water temperature and moon luminosity. Alewives entered Black Creek primarily at night.


Lake, T.R and R.E Schmidt. 1997. Seasonal presence and movements of fish populations in the tidal reach of Quassaic Creek, a Hudson River tributary (HRM 60): Section VII, 36 p. Final Reports of the Tibor T. Polgar Fellowship Program, 1997. Hudson River Foundation, NY.

Schmidt, R.E., K.E. Limburg and T. Stillman. 1994. An estimate of the significance of tributary spawning of alewife (Alosa psuedoharengus) in the Hudson River estuary. pp. 23-35. Final Report to Hudson River Foundation, NY.

Previous studies

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.