Since 2012, the Mystic River Watershed Association has been working with hundreds of volunteers to count river herring passing through the fish ladder at the Mystic Lakes Dam to spawn in Upper Mystic Lake. In 2017, ninety trained citizen scientists counted the largest number of herring since the monitoring program began, documenting another strong Mystic River herring migration at an estimated 630,000 fish!
This run size represents a considerable increase from last year. We speculate that the reason for this, at least in part, is that the herring that were born in the Upper Lake (or further upstream), are now sexually mature and have returned to reproduce (generally at 3 years).
The herring monitors logged an impressive 791 counting periods completed over 81 days, resulting in 91,997 herring counted this year. This data is then shared with the Massachusetts Division of Marine Fisheries, who uses a model to determine the estimated run size: 630,098 +/- 60,599 herring!
River herring collectively refer to two species of herring, Blueback (Alosa aestivilis) and Alewife (Alosa pseudoharengus). These two species are referred to as “anadromous” fish as they live the majority of their life in salt water but lay eggs (spawn) in fresh water. The billions of river herring eggs that are produced in Upper Mystic Lake will develop into juvenile herring within just a few days. These juveniles will stay in the fresh water for up to 4 months before swimming downstream to live in estuarine waters. The river herring that survive will reach an age to reproduce after 3-4 years and usually return to the same waters where they were born.
MyRWA would like to thank all of the herring monitors for making this program possible, as well as the Massachusetts Department of Conservation and Recreation and Massachusetts Division of Marine Fisheries!