This spring, over 70 of our devoted volunteers spent more than 130 hours watching and waiting for river herring to make their way upstream to their annual spawning locations from March 25th – June 11th. The first fish was seen on April 11th at Herring Brook. As the runs ramped up from there our volunteers counted a total 11,022 fish passing our monitoring sites this season.
The work of our volunteers has been key to the detection of river herring population changes, and the data they collect support population estimates that can give scientists and ecosystem managers alike a better clue into protecting these fish. We would like to extend a huge thank you to our dedicated volunteers for your part in making an impact!
2024 RIVER HERRING RAW DATA COUNTS AND POPULATION ESTIMATES
Raw counts are the number of individual fish that are directly observed and recorded by volunteers. The raw counts are dependent on both the number of fish and also the amount of time we spend watching for them. So they need to be viewed through that lens. Still, they provide direct insight into what our volunteers are seeing in the field. The raw count data is then sent to the Division of Marine Fisheries (MA DMF) and aggregated into an algorithm that estimates population size. It is important to note that counts of “zero” does not mean that there are no herring in the system. It can often mean that the fish are just just hiding from predators in the natural environments available to them. When dams or fish ladders are present they block or funnel fish into enclosed spaces where they are easily visible. In natural river conditions it can often be very hard to see the fish that are unconstrained and pass freely. In other cases the zeroes really do reflect an impairment in the habitat. In all cases, the “zero” counts are just as valuable as any other data point and we use them to understand the longer term trends.
INDIVIDUAL SITE DISCUSSION
Bound Brook – Scituate and Cohasset
Bound Brook is unique in that it is affected by the Hunters Pond dam that was removed seven years ago. As with many of our dam removal projects in systems that had extirpated herring populations, we have seen them struggle to recover as the only fish that enter the system are “scouts” exploring new streams. Still, there is hope for more coming into the system, especially since herring that pass the Hunters Pond site have passage via two fish ladders to a large amount of habitat in the Aaron River Reservoir, as well as renewed interest in reinvigorating this herring population.
First Herring Brook – Scituate
Counts at First Herring Brook have been hanging in the low numbers since flow was restored to the Old Oaken Bucket fish ladder in 2012. 2024 was an exciting year at this site even though the ‘official’ numbers were low. Only 2 fish were seen passing up the ladder during an official count. However, NSRWA staff, interns, volunteers, and MA Environmental Police reported seeing additional fish below the dam and even entering the ladder. This documentation is crucial to NSRWA’s work with the Town of Scituate to continue to provide flows for herring and instream habitat, and is working on expanding potential habitat by improving access to the reservoir upstream.
South River – Marshfield
Volunteers at the South River did not see many herring at the Veterans Memorial Park fish ladder this year, only 11, which matched the 2023 count. This year was the end of an era as the Town of Marshfield is slated to remove the Veterans Park Dam beginning in late 2024. Next year will be our first opportunity to see what the restored stream will mean for South River herring populations.
Third Herring Brook – Norwell
This year we moved the counting location upstream to a spot behind the Hanover Mall. This location is intended to verify if fish are making it up past all of the dam removal sites on Third Herring Brook. While we didn’t see any fish this year, we did spend considerable time with MA DMF ensuring that free passage is available. We will continue that work into 2025.
Herring Brook – Pembroke
Herring Brook is home to our most robust herring population – this year volunteers counted 11,009 herring passing the ladder, which is almost twice as many as 2023 and 48 times as many as 2022! This continues to be one of the largest runs in the state and is an inspiring place to watch the spring migration.
MA DMF also operates an electronic counting device on Herring Brook. This counter is able to count every fish that passes by, including times when our volunteers are not there (especially overnight). This data is considered the “true population” and is an excellent compliment to the estimates we get from our volunteer counts.
Thank you again to all of our volunteers – we hope you will join us in 2025!
Click here to read more about River Herring Counts.