Herring Decline Mystery Spawns New Studies

            Throughout the coastal waters of New England, the annual migration of river herring has been a seasonal “must see” event. Watching thousands of small fish swim upstream to natal waters, traveling from saltwater oceans to freshwater streams and ponds, is one of nature’s miracles. Yet these marine animals, like most living things on the plant, have been negatively impacted by human activity. But is that the whole story?

            On April 29, Alewives Anonymous, Inc. held its annual meeting. The group was founded in 1984 to promote and educate the Tri-town communities of Marion, Rochester, and Mattapoisett about all things alewives, more commonly called herring. After enjoying a homemade supper of chowder, stuffed quahogs, and apple cobbler, President Arthur Benner gave his report.

            His report listed herring migration survey counts since 1988, the first year an electronic counter was employed. Over the past 31 years, herring counts have declined to a discouraging low, despite intermittent glimmers of hope. For instance, in 1989, 39,938 fish were counted at the confluence of the Mattapoisett River at Snipatuit Pond, with spikes as high as 130,296 between 1998 and 2000. The 2018 count, however, was a meager 5,241.

            With moratoria in place for the past several years, the group is seeking to better understand natural and manmade stress factors in the hope that, with good data and marine science, these tiny fish can be saved.

            Guest speaker Christopher Rillahan, a doctoral student from the University of Massachusetts at Dartmouth, has been studying herring migration since 2017 in both the Tri-town area and Cape Cod. Rillahan’s observations and studies were aided by the use of sonar imaging equipment that granted visual clarity to what was going on with herring populations during the migration. But, moreover, Rillahan pinpointed when the fish were most actively moving through the river systems.

            Historically, Rillahan said, herring counts were conducted during a 12-hour daylight sampling when it was believed the fish were most active. What the sonar uncovered was herring activity during sunrise and sunset.

            Displayed on the screen, the audience witnessed the herring swimming in large balls through counting areas in the morning and evening, images that heretofore could not have been seen. Over several migration seasons in both Mattapoisett and on Cape Cod, Rillahan confirmed the herring movement in those two times of the day. But he also found other surprising information. Could something else be impacting herring stocks besides the possibility of counts being off a bit? It had long been established that commercial fishing had been a prime suspect. Maybe there were others.

            What Rillahan found was the presence of predator fish, primarily striped bass and bluefish, patrolling the herring well upriver from the ocean. And then there are the cormorants. The sonar images clearly found the fast-moving birds darting at the herrings’ movement. And last but not least, there was also one massive snapping turtle.

            Rillahan said the southeast is a major area for herring study, and counts take place primarily in April. It is now understood that volunteers counting fish may be missing a large percentage of the migrating fish due to nighttime activity.

            Another area not well understood, Rillahan explained, is what becomes of a herring after it has spawned. He said earlier studies noted herring would spawn at four years of age or older. Today, most spawning fish are only two years of age, causing scientists to scratch their heads. Why has it changed, and where are the mature fish? Are there mature fish?

            “The life of the river herring is far more complex then previously believed,” Rillahan stated. He said his studies of data continue, and he hopes to provide further critical information in the coming months.

            To learn more about river herring, you may visit www.riverherringnetwork.comwww.greateratlantic.fisheries.noaa.gov, or www.plumblibrary.com/services/alewives-ananymous.org.

By Marilou Newell

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