Page 4 THE REVERE ADVOCATE – FRIDAY, NOVEMBER 11, 2022 2022 MYSTIC RIVER HERRING RUN LARGEST IN THE STATE MYSTIC RIVER HERRING RUN 2022: 425,000+ A ccording to the offi cial estimate from the Division of Marine Fisheries (Mass DMF), more than 425,000 river herring passed through the fi sh ladder at the Mystic Lakes Dam in Medford in 2022, and an additional 20,000 passed into Horn Pond. This the highest documented herring run this year in any river in Massachusetts! River herring — Alewife and Blueback herring — are migratory species that spend most of their lives in the open ocean, but return to freshwater every year to spawn in the river system they were born in. They are threatened by overharvesting in the ocean and — crucially — by the loss of inland habitat for breeding caused by dams blocking access to inland lakes and streams. The recent count represents the latest chapter in an ecological restoration success story that has included the installation of multiple fi sh passages on the river resulting in a sharply rebounding population of river herring in the Mystic River. HER R ING NUMBERS IN CONTEXT This year’s total is a bit lower than last year’s estimate but consistent with the sense that the Mystic population remains robust. (Fish populations fl uctuate over time for multiple reasons). Often the Mystic is among the largest documented herring runs in the state, but this year it was the largest. This is both remarkable and a sign of some less positive changes elsewhere. It is remarkable because one might not expect the largest herring population in the state to be one that has to run the urban gauntlet of Boston Harbor and the Amelia Earhart Dam — not to mention the Mystic Lakes Dam — to get to their breeding grounds. Usually, the largest runs in Massachusetts are on rivers with relatively unobstructed streams and protected estuaries like the Herring River in Wellfl eet on Cape Cod Bay. But this year, numbers from herring counts from other usually high-count Massachusetts sites were notably lower than last year. The Herring River count, for instance, was 290,000, after counts of over 1,000,000 as recently as 2019. As Ben Gahagan of the Division of Marine Fisheries says, “Indeed it was a bad year across most of southern New England.” Similar patterns were seen in Rhode Island and Connecticut. “On the other hand,” Gahagan adds, “Maine had record runs and New Hampshire was actually pretty decent." That is, there may be some phenomenon at work disproportionately aff ecting southern populations in recent years. Multiple causes may Lakes Dam in Medford was built in 2012 — allowing fi sh in the Mystic River to reach Upper Mystic Lake for the fi rst time in decades. At that time, the Mystic River Watershed Association launched a volunteer herring count in collaboration with Mass DMF. Dozens of volunteers annually visit the dam to make 10-minute sampling counts of fi sh passing into Upper Mystic Lake every daylight hour from be at work, and state scientists say it is too soon to point to a single reason. One major factor in reducing Massachusetts herring populations in recent years might be the droughts the area has experienced. In many river systems, droughts late in the summer can prevent juvenile migration back to the ocean by drying up streams, reducing productivity in the population in a way that is seen years later in the fi sh counts of returning adults. The Mystic system may be relatively immune from this eff ect, at least currently. There are fewer dead ends for fi sh to end up in, even in relatively severe drought. MORE ON THE ECOLOGICAL SUCCESS STORY A fish ladder at the Mystic April to June, and the data are used to estimate the total number of fi sh passing through the fi sh ladder. In the fi rst year, an estimated 200,000+ fi sh passed through the dam, based on data generated by volunteer counters. But river herring fi rst return to freshwater to reproduce only at age 3 or 4, when they are sexually mature. When the fi rst cohort of fi sh born in the newly expanded freshwater habitat reached reproductive age and returned for the fi rst time to Mystic Lakes in 2015, volunteer counts showed that the population of fi sh loyal to the Mystic River had doubled (Figure 1). And numbers continued to climb over the next few FISH | SEE Page 15
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