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Peconic River Fishways: Making the Insurmountable Surmountable

Estuaries are renowned for their habitat value, supporting 80-90% of recreational fish species during some or all of their life stages.  They are sometimes called the “nurseries of the sea” because their sheltered, fertile bays and tributaries provide ideal locations for spawning and juvenile growth.  The Peconic Estuary is no different – scores of marine fish call the Peconics home. 

However, the productivity and beauty of estuaries has not gone unnoticed by another species – humans.  In some cases, humans have altered the environment to the detriment of other species.  One example is the effect of manmade dams on diadromous species.

Dams vs. Fish
In the late 1800s and early 1900s, dams were built on the tributaries of the Peconic Estuary for grist mills, cranberry bogs, other industrial uses, and even as property line demarcations.  Overnight, historic migratory routes of diadromous fish were cut off, blocking access to hundreds of acres of habitat.

Diadromous fish in the Peconics include river herring and American eels.  Alewife are the most common river herring in the Peconics. They are anadromous; locally, adults migrate up the Peconic River each year in early spring (late February-April), spawn, and return shortly thereafter to the continental shelf (approximately 60 miles offshore in the ocean) where they spend the majority of their adult lives.  Like salmon, alewife home to their natal river (i.e., the river where they were born) to spawn. American eels are catadromous and as such have a much longer residence in the Peconic River and other tributaries - as long as thirty years. All American eels are born in the Sargasso Sea, a two-million square mile area in the western North Atlantic; their choice to spend their lives in the Peconics is thought to be based entirely on chance. Unlike alewife that spawn each year, American eels make only one spawning migration back to the Sargasso; they die following reproduction.  

Both alewife and eels are critical parts of the estuarine food web as important prey species of predatory fish (e.g., striped bass, bluefish) and birds (e.g., heron, osprey). Both species are also important to directed commercial and recreational fisheries, targeted either for food or use as bait.  Unfortunately, both species have experienced dramatic declines in recent years.  The 2003 commercial catch of American eels in the Atlantic was at the lowest level since record keeping for the commercial fishery began in 1945.  Likewise, commercial catch of alewife and blueback herring on the Atlantic coast declined 90% from 1985 to 1998.  The American eel population is thought to be so compromised that it is currently under review for listing on the U.S. Endangered Species Act.  Habitat reduction and degradation, including blockage to upriver migrations by dams, are cited as significant factors in the declining numbers of alewife and eels.

Fishways: Helping Eels and Alewife Over the Hurdles
Fortunately, with a little engineering and a lot of dedication by local citizens and governmental partners, it is possible to help eels and alewife over the dams.  Removal of obsolete dams is often the most desirable option, both from financial and ecological standpoints.  In cases where removal is not feasible due to concerns about water level, historical value of the dam, etc., fishways are the next best alternative.  Fishways come in all shapes and sizes – galvanized steel steep pass fish ladders, step pools, rock ramps, and bypass channels, to name a few.  Regardless of style, their function is the same:  to help migrating fish get from the bottom of the dam to the open habitat at the top of the dam.

There are four main dams on the Peconic River.  At 17 miles long, the Peconic River is the longest river on Long Island and the major tributary of the Peconic Estuary.  The dams going upriver are as follows:  Grangebel Park, Upper Mills, Forge Road, and Edwards Avenue.  There is another dam at Connecticut Avenue.  The Peconic River is tidal upstream to the base of the Grangebel Dam.  The Grangebel Park Dam is an earthen dam that has two separate spillways or waterfalls, one each on the north and south channels that wind through the park.

The above graphic shows the locations and pictures of the 5 main spillways on the Peconic River. Note that the photo of the Grangebel Park North Spillway was taken when the fish ladder was installed.

In 1996, a group of concerned citizens led by Bob Conklin, a retired Riverhead school teacher, got together to discuss strategies for restoring upstream fish passage on the Peconic River.  Soon the Peconic River Fish Restoration Commission was formed.  Members researched emerging fishway technology and traveled throughout New England to see various structures already in operation.

Their efforts were rewarded in 2000 as Miller Environmental installed a steep pass fish ladder at the North Spillway in Grangebel Park.  As soon as the ladder was in place, alewife started up the structure.  That spring, alewife successfully migrated upriver of the dam for the first time in 100 years.

Although the fish ladder has been successful at passing fish, it is a significant maintenance burden due to its required seasonal installation and tendency to get clogged with debris in the busy park. As a result of over 10 years of dedicated planning and persistence and nearly $1million of funding, a new permanent rock ramp was finally constructed at the South Spillway in Grangebel Park in 2010. The rock ramp, which will now pass American eels as well as alewife (steep passes only pass alewife) and looks like natural rapids rather than something manmade, opens 24 acres and 1.5 miles of diadromous fish habitat. Check out the recent front-page coverage in Coastal America's newsletter, click here to view.

The Fishway Team
The 90-member Peconic River Fish Restoration Commission is citizen-driven and is largely to credit for this exciting initiative. The Town of Riverhead, NYS Department of Environmental Conservation, U.S. Fish and Wildlife Service, American Rivers, FishAmerica, National Oceanic and Atmospheric Administration, and the Corporate Wetlands Restoration Partnership are also major players. The Peconic Estuary Program has found a niche in fundraising for the fishway efforts. Working closely with the Town of Riverhead, we have already secured over $1,000,000 for fish passage at the first two dams and are moving our efforts up the Peconic River and now branching out to other historic runs in the Peconic Estuary.

Fish Passage into the Future
Our ultimate goal?  To make all the insurmountable dams in the Peconic Estuary surmountable.  There are many tools in the toolbox, and we plan to explore them all for each of the manmade barriers throughout the estuary, both on the Peconic River and beyond.  Over 300 acres of critical fish habitat will be restored once the entire Peconic River is re-opened to fish migration.  There are approximately 50 other tributaries in the Peconics that may have dams that block historic fish migratory routes.  Our plan is to discover them, devise a remedy, and help the fish over the hurdles.

Please Help Us Help the Fish!

  • Are you aware of additional barriers to fish passage, such as dams and culverts, on other rivers in the Peconic watershed? If so, please let us know the location so we can add it to our inventory. Call 631-852-5750 or e-mail
  • Interested in joining a cutting-edge, community-driven effort that is achieving positive and tangible environmental results? Join the Peconic River Fish Restoration Commission!



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