The importance of alewife runs on Long Island’s ecosystems and beyond


via Gfycat

Story & photos by Luke Ormand |

One sure sign of spring on Long Island is the return of the beloved osprey, our favorite snowbirds outside of our grandparents.

On extended wings, these birds begin to show up in mid- to late-March, setting up their territories (increasingly overlapped by bald eagles) and tending to their nests, which are often in dire need of repair and embellishment.

But have you ever wondered why the Osprey return at this time of year?

It turns out their migration north coincides with the migration of another sign of spring — the alewife, also known as the river herring. 

Alewife are known as anadromous fish. They live their lives out at sea, but return to freshwater systems to spawn, like salmon and striped bass. Their return is triggered by many factors, including water temperature and moon cycle.

When the stars align, these fish congregate together and swim up our rivers and creeks toward lakes and ponds to reproduce before returning to sea.

But there’s been a decades-old problem for these fish along Long Island’s coastlines.

Our rivers and streams have been heavily modified to make human lives easier. Dams, weirs, culverts, bulkheads and other structures often impede the ability for these fish to move upstream.

Historically, rivers were dammed in order to build mills (example: Lower Lake in Yaphank), to harvest ice in the winter (Old Ice Pond at Quogue Wildlife Refuge) or to create harvestable cranberry bogs (various stretches of the Peconic River). 

The original intentions for creating these impediments are no longer needed, yet the blockades continue to prevent migration. 

During big alewife runs, as the migrations are often called), large schools of fish will congregate, swimming in tight circles searching for a way upriver, which makes them easy prey for the osprey, hungry from a long voyage north. 

Alewife are also an important food source for raccoons and river otters (which are slowly repopulating Long Island) where they can be caught from the shoreline.  Come mid-March, naturalists, nature lovers and conservationists often check in on a dammed section of the Peconic River, which acts as a bellwether for the start of migration. 

This particular section of the river does not benefit from a fish passage, though dedicated scientists spend the time to scoop and measure the fish before moving them to the upper reaches of the tributary to help them complete the cycle.

On a recent visit to this not-so-secret location, the sky was overcast and the water dark.

Rushing water spilling over the dam made it near impossible to see beneath the surface, but there were signs that the river herring had arrived. 

The smell of fish hung in the air and after a quick scan of the shoreline, it was clear why.  Raccoons are excellent at catching these fish and the remnants of last night’s dinner can often be found on the banks of the freshwater pool.

The unmistakable chirping of the osprey also fills the air, as these birds circle above, focusing on their prey below — waiting for the right moment to strike.

When a waterproof camera is dipped below the quick moving water, a whole new world is revealed. River herring, numbering in the hundreds, are swimming orderly against the current, compelled by the forces of nature to continue their journey despite the blockade before them. 

Without our help, these fish who are linings up along our shore’s creeks and rivers will be prevented from completing their life cycle and will return to the sea or die before being given a chance. 

In an effort to help the alewife population stabilize and ultimately recover, governments, not-for-profits and concerned citizens have put in tremendous efforts into removing these obstructions or, where practical, providing fish passages to allow for safe travels upstream.

One of the most prominent fish passages (also known as a fish ladder) is located along the Carmans river, where Hards lake was dammed just north of sunrise highway at Southaven County Park.

This passage, which can be seen from Victory Avenue, is a large metal structure that allows these hardy fish to climb the cascading water and enter Hards Lake and the upper portions of the Carmans river to spawn. 

A short while later — less than a week — these eggs will hatch and the young of the year will quickly grow in the freshwater habitat until they move back down the fish passage to our bays and ocean.

In addition to the utilitarian, metal box fish ladders which are featured along a number of Long Island’s rivers, there are other designs that provide access for diadromous fish and enhance the aesthetics of the site. 

For instance, a “natural” rock ramp consists of large stone and cobble, mimicking a natural stream bed like those typically found in the wilds of upstate New York.

Riverhead’s Grangebel park is the best example of this style on Long Island, and it has proved exceptionally successful as demonstrated by ongoing research and observation by Seatuck Environmental Conservation and the state Department of Environmental Conservation.

Ladders or passages have been successfully installed all around Long Island as conservation efforts and awareness have increased over the years. 

Some sites where the public can see these passages are: Massapequa Lake in Massapequa, Argyle Lake in Babylon Village, Penataquit Creek in Bayshore, Canaan Lake in Patchogue and a brand new passage at Hubbard County Park in Flanders. 

It’s especially important these fish and their young find their way back to sea, because not only are they food for landside animals, they are a critical part of the food chain that sustains larger fish and, ultimately, long-struggling sea mammals such as whales.

So what can you do to help restore these fish populations and their natural habitats?

For one, Seatuck has put together a comprehensive plan, called the “Long Island Diadromous Fish Restoration Strategy.”  

This document discusses the historic range of these fish on Long Island and breaks the streams, rivers and tributaries down by town.

You can call on your local politicians and favorite conservation groups (such as Save the Great South Bay) to work toward implementing this plan and restoring the flow of our rivers and streams and ensure the recovery of river herring, American eels and sea-run brook trout.

The next time you drive over one of the Island’s rivers or creeks or the next time an osprey flies into your field of view, take a minute to think about the humble river herring and what you can do to help them survive for generations to come.