The Fish in Your River
February 19th, 2013 | by Cynthia
Imagine the Ipswich River prior to development and the construction of dams; the river and its tributaries were free flowing, with abundant riffles and pools. The river supported diadromous (migrating between fresh and salt water) fish runs numbering in the millions. The river supported such fish as Alewife and Blueback herring, Rainbow smelt, Atlantic salmon, Striped bass, American shad, Sea Lamprey, sturgeon and American eel. In fact, the river’s original name, Agawam is a Native American term meaning “place where fishes of passage resorted” which is indicative of the prior abundance of migratory fish. The harvest of alewife (river herring) as far upstream as Wilmington was an important part of the local economy, and Wenham Lake, now a public water supply reservoir, was the most important alewife nursery in the region. The water temperatures were also consistently cold and high in dissolved oxygen, supporting species that require flowing waters or “river fish” such as Eastern brook trout, White sucker, Fallfish, Creek chubsucker, Johnny darters, White perch, Rainbow smelt, shad and Atlantic salmon that depend on flowing water.
Today, the Ipswich River is heavily impacted by low flows (from water withdrawals for public drinking supply) and dams, which impact the native fishery. Fish species that require flow are at a disadvantage, and the river is dominated by generalist species that can tolerate warm water and ponded conditions, mainly redfin pickerel, American eel and pumpkinseed. These “pond fish” currently make up over 80% of the fish biomass in the river.
Today, the Ipswich Mills Dam is a relic of our early industrial past. The current fishway, rebuilt in 1996, allows some river herring, sea lamprey and sea run trout to ascend into the pool behind the dam but like all fishways is only partially effective. Other migratory species such as rainbow smelt and American shad will not use the fishway at all. A team of economists and fish ecologists recently found that in spite of state-of-the-art fish passage facilities on major Northeast U.S. waterways, including the Merrimack and Connecticut rivers, actual numbers of fish passing through them over several decades reached only a tiny fraction of targeted goals.
In an attempt to measure success at the Ipswich Mills Dam fishway, the Ipswich River Watershed Association’s annual Fish Count monitors herring using the fishway to enter the river above the dam. From April 1 to mid-June volunteers perform 10 minute counts throughout the day at the top of the fishway looking for fish like herring, shad or lamprey. The data are used to document the conditions under which these fish migrate into the Ipswich River to spawn.
Since monitoring began in 1999, the most river herring observed in the Ipswich River was 133 fish in 2008 This is a tiny fraction of the historic herring run for this river but we are not alone; according to the Herring Alliance some river herring runs on the Atlantic Coast have declined by 95% or more over the past 20 years. In 2006 the National Marine Fisheries Service designated river herring as a species of concern. Population decline may be associated with numerous factors including by-catch, habitat loss and degradation, water pollution, access to spawning habitat, and natural predators. We hope that through participation, volunteers will increase their understanding and stewardship of the Ipswich River and the fish species it supports.
To find out how to help protect river herring by participating in the annual fish count, contact the Ipswich River Watershed Association at (978) 412-8200 visit our website www.ipswichriver.org or find us on facebook, facebook.com/ipswichriver.
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