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'Eel Spearing in Setauket' by William Sidney Mount

By John L. Turner

This is part two of a two-part series on a remarkable pair of fish. 

The life cycle of the American Eel is a bit more complicated than river herring and consists of six stages: egg, larvae, glass eel, elver, yellow eel, and silver eel. 

Mature adults reproduce just once in their lifetime with all the eels emanating from the East Coast unerringly migrating to the Sargasso Sea where mass spawning takes place. (The Sargasso Sea, situated south of Bermuda, has no land borders but is distinct by being bounded by four strong ocean currents, including the Gulf Stream, resulting in quiet waters entrained within the gyre; here masses of sargassum weed abound giving shelter to many marine species including hatchling sea turtles). 

Shortly after spawning here the adult eels die. A grown eel releases as many as several million eggs and they hatch within a week. At first the leptocephali don’t look eel-like, being transparent and flattened, described as looking like a willow leaf; they are carried north by the currents, including most notably, the Gulf Stream. 

American Eel. Wikipedia photo

After about half a year they metamorphose into “glass eels,” still transparent but shaped like baby eels, and this is the stage, along with the slightly pigmented elver stage, that arrives at the mouths of Long Island’s streams. They wriggle their way up vertical faces and over wet land to make their way into freshwater ponds and lakes (although some spend their adult lives in brackish waters of Long Island’s estuaries).

While living for decades in ponds and lakes they move through a few more color stages, including yellow and silver eels. Here they become fully integrated members of the local food web, feeding on a variety of different aquatic prey while being preyed upon by many other animals including ospreys and bald eagles (stay tuned: June’s “Nature Matters” column!). 

Eels are also food for humans (remember one of Long Island’s most famous paintings  — William Sidney Mount’s 1845 “Eel Spearing at Setauket”?). Eventually some internal trigger “tells” these decades-old fish to head to the ocean and back to the Sargasso Sea to create a new generation of eels. To assist them in their long journey their bodies change a little — their eyes enlarge as do their pectoral fins.

Eel are managed by the Atlantic States Marine Fisheries Commission (ASMFC), beginning in 2006 with the first species management plan. The Commission sets harvest quotas for all age classes of eels including those to be used as bait and for direct consumption. The news has not been good over the past several decades with eel abundance on the decline and ASMFC currently classifies the eel stock as “depleted.” 

Ways to increase abundance? Reduce all causes of eel mortality, especially among younger animals, among adults trying to navigate the perils of turbines at hydroelectric dams and increase opportunities for eels to migrate to freshwater areas where they can survive, becoming mature adults through time.

The Seatuck Environmental Association has been at the forefront of documenting the migratory occurrences of Long Island’s alewives and eels through its signature river herring and eel surveys and has, for decades, been working to protect existing runs while facilitating others. If you want to participate in trying to find new sites of alewife runs or eel migration or document more completely whats’s happening at existing sites, go to Seatuck’s webpage.

In pre-colonial times, before the advent of dams and other obstructions, many, if not all, of Long Island’s streams and rivers likely teemed in Spring with alewives and eels. They, in turn, provided nourishment to many species of wildlife from otters to ospreys to eagles. However, the Long Island of today is a very different place, with so many ecological threads severed or frayed. The reduced abundance of these fish illustrate the pervasive loss of ecological connectivity that has occurred on Long Island in the past few centuries. The good news? Many individuals, organizations, and governmental agencies are working to enhance connectivity here – to reconnect severed ecological threads – through the installation of additional ladders and passageways, and better yet, the removal of more dams, all steps to give these remarkable animals a chance to recover and perhaps even prosper.

I hope you make their acquaintance.

A resident of Setauket, John Turner is conservation chair of the Four Harbors Audubon Society, author of “Exploring the Other Island: A Seasonal Nature Guide to Long Island” and president of Alula Birding & Natural History Tours.

Above, alewives at Woodhull Dam in Riverhead. Photo by Byron Young

By John L. Turner

This is part one of a two-part series on a remarkable pair of fish. 

Each Spring, driven by impulses and guided by signals not fully understood, they migrate to Long Island to create the next generation. But unlike red-winged blackbirds, with their bright red shoulder patches and reedlike konk-a-ree calls, or Spring Peepers with their distinctive “sleigh bell” calls ringing from recharge basins and wetlands around Long Island, these migrating animals arrive quietly, their arrival and presence unknown to almost all Long Islanders. And while we may not be aware of their arrival, many other animals like bald eagles, ospreys, otters and great blue herons certainly do.

What animals might they be? Fish — or more precisely alewives (Alosa pseudoharengus) [meaning false herring], a species of river herring, and American Eel (Anguilla rostrata), one of nineteen species of snakelike fish with a worldwide distribution. Alewives return as adults to Long Island waterways, ranging from 9-12 inches long, while eels arrive as “babies,” just several months removed from their birth in the open ocean. Alewives are a shimmering silver in color with a distinctive dark spot behind the gill cover and are almost indistinguishable from their cousin, the blueback herring. When small, eel are translucent, gaining pigment as they mature.


Photo by John Turner

These species are diadromous fish, “dia” meaning “through or across” and “dromous” meaning ”running,” a reference to the migratory habit of these fish moving between the two worlds they inhabit as part of their life cycle — freshwater and saltwater. Alewives and other river herring develop and mature in the salty waters of the North Atlantic, moving into freshwater systems to spawn, while eel typically develop in freshwater and spawn in salt water, in the famous stretch of the mid-Atlantic Ocean known as the Sargasso Sea. 

To be more specific, biologists segregate diadromous fish into two other categories: anadromous fish like alewives, other river herring such as American Shad, striped bass, and salmon which mature in salt water but move upstream (“ana” meaning upward) to spawn in freshwater, and catadromous fish (“cat” meaning downward) such as American Eel which develops in freshwater but moves downstream to spawn in salt water.

Schools of alewives, three to four years old, seek out the freshwater stream of their birth, apparently finding their natal stream by its unique and distinctive chemical scent, although fishery biologists are not sure of the precise mechanism they use that allows them to find their way. Once these river herring find suitable habitat they spawn, depositing from tens of thousands to hundreds of thousands of eggs, and the adults soon leave to head back to the ocean. The eggs left behind hatch and the young develop over many weeks before, in mid-summer, heading out to open water too.

Cued by warming waters silvery, shimmering schools of alewives (and smaller numbers of their cousin, blueback herring) arrive in Spring — typically from late March to early May — congregating en masse at the mouths of many streams around Long Island. They then move inland and the “run” has begun! (For a wonderful account of alewife runs and their importance to colonial America, I encourage you to find a copy of The Run by John Hay, published in 1959). 

A fish ladder on the North Shore. Photo by John Turner

Several hundred years ago the days of “alewife runs” were a time of great excitement for local residents as the fish provided them with an abundance of food at a critical time of year, but also as food for swine, and fertilizer for crops, most notably for “fish corn,” the practice of burying a piece of a fish (often the head) under the planted corn kernel. The rotting fish provided nutrients and minerals to the corn stalk as it grew, a practice originating with Native Americans.

Alewife runs were so important that some of the earliest wildlife laws in the United States were enacted to protect them. A very early law, passed in 1709 in Massachusetts stated: “That no wears [weirs], hedges, fishgarths, kiddles, or other disturbance or encumbrance shall be set, erected or made, on or across any river, to the stopping, obstructing, or straightening of the natural or usual course and the passage of the fish in their seasons, or spring of the year, without the approbiation and allowance first had and obtained from the general sessions of the peace in the same county”. Another law, adopted several decades later in 1741, related directly to the fish: “to prevent the destruction of the fish called alewives, and other fish.”

Their original abundance, especially when contrasted with current levels, was marveled at. John Waldman, a fisheries biologist whose book Running Silver, a wonderful treatise on migratory fish, has noted this abundance by numerous historical references. One account, from 1634, notes: “Alewives came up to the fresh rivers to spawn in such multitudes it is almost incredible, pressing up such shallow waters as will scarce permit them to swim.” Another quote nearly one hundred years later in 1728, noting alewife abundance in Virginia, says: “In a word, it is unbelievable, indeed, undescribable, as also incomprehensible, what quantity is found there. One must behold oneself.” The abundance of alewives today is a tiny and pale shadow of what once existed.

Unfortunately, many obstacles confront alewives and eels today on Long Island as they attempt to move upstream to spawn — not the aforementioned weirs, fishgarths, and kiddles of old, but dams, dams, and more dams (also other structures like poorly designed road and railroad culverts). 

Constructed to channel water for the operation of sawmills, grist mills, and woolen mills, and to create impoundments for growing cranberries and harvesting ice, these dams and culverts have almost entirely foreclosed the ability of these fish to pass unimpeded in streams here. The stream at North Sea, Alewife Brook, draining Big Fresh Pond and emptying into North Sea Harbor is one of the very few remaining free-flowing, unimpeded streams remaining on Long Island (and one of the best places to visit to see alewife runs).

The response to solve the dam problem has been the construction of fish ladders or ramps on and around the obstacles. Fish ladders and rock ramps, angled so the fish can make it from the lower stream section to the higher water levels in the upstream impoundment, has proven to be an alternative and somewhat effective strategy for river herring to gain access to spawning areas. To assist eels, pegged boards or tangled rope netting have been deployed which the young eels can wriggle up. 

Fish ladder (on right) and eel passage (on left) on the Peconic River. Photo by John Turner

Ladders and ramps have been placed on the main stems of the Peconic and Carmans Rivers, as well as the Swan River in East Patchogue, Massapequa Creek in Massapequa, and another at Betty Allen Park in Huntington. Two important ladders (due to the amount of freshwater the ladders will access) are being constructed — one on the Woodhull Dam in Riverhead providing access to an entire tributary of the Peconic River and another at the base of Mill Pond in Rockville Centre. A ladder is in the planning stage for Bellmore Creek which is expected to be installed in 2023.

A more effective but more controversial solution is dam removal. In many places in the United States dams have been removed but on Long Island this has not been the case as pond-side homeowners fear the loss of their physical and visual access to the water. 

One possible area of success is at West Brook within Bayard Cutting Arboretum in Oakdale where the Seatuck Environmental Association has been advocating for the State Parks to not reconstruct the concrete dam that failed on the stream. The dam failure has opened up more than a mile long stretch of West Brook that heretofore was not accessible for migratory fish.

*Part two of this series will appear in the issue of May 12.

A resident of Setauket, John Turner is conservation chair of the Four Harbors Audubon Society, author of “Exploring the Other Island: A Seasonal Nature Guide to Long Island” and president of Alula Birding & Natural History Tours.