Baby Glass Eels in New York Harbor

The last Monday of April brought with it sights of Box Turtles, Least Terns, songbirds beginning to nest, and queen bumblebees flying in zigzag motions searching for a safe place to nest. All signs of spring and driven by lengthening daylight and warmer air and water temperatures.

The last Monday of April also brought with it the sight of baby eels swimming in New York Harbor. An exciting moment to catch sight of a tiny American Eel after it has taken a perilous journey drifting with the Gulf Stream and other currents for about a year to reach the urban-suburban waters of Lower New York Bay and surrounding tidal waters.

It was day one of a long-term research project to study and document the spring migrations of American eels and river herring in New Brunswick along Lawrence Brook, a tributary of the Raritan River. A joint research project being conducted by the Lawrence Brook Watershed Partnership, the City of New Brunswick Water Utility, the New York-New Jersey Harbor & Estuary Program, and the National Oceanic and Atmospheric Administration (NOAA).

Found swimming in the brook this day were a pair of baby eels, only  a few inches long, called “glass eels.” The term “glass eel” is defined as a juvenile American Eel  that has transformed from a larvae stage into a transparent fish that looks clear as glass. The near lack of any pigment on its body has earned this baby fish the name "glass eel."

You can actually look through the eel! An amazing sight to see, a form of life so fragile and complex. To me the little delicate eel looked liked a string of spaghetti or a small leaf of a willow tree with tiny black eyes, a small mouth and red gills. Really cute, if you like baby fish.

The little glass eels and a number of herring splashing around (either Alwewife of Bluebacks) were seen upstream near a  dam, which is a barrier to eel and fish migration. Part of this research project is a fish passage feasibility study, which would perhaps open up around three miles of habitat to migratory fish.

Local fisheries biologists, Kenneth Able and Michael Fahay, write in their book, The First Year in the Life of Estuarine Fishes in the Middle Atlantic Bight, that young eels will drift in the ocean for up to a year, during which time the Gulf Stream and other ocean currents transport the tiny eels northward away from the Sargasso Sea where they were born over six months ago. Sometime starting in February the young eels leave the ocean currents and swim fast and furious towards the coast. Glass eels are strong swimmers and as currents take them close to the continental shelf and coastal waters, they will swim toward the coast to seek out estuaries. Sometime in the spring, the little glass eels enter New York Harbor and will spread out. Some will stay in saltwater, while others will swim up small creeks and large rivers in freshwater systems, including the Hudson River, the Raritan River, the Navesink River and their tributaries.

Juvenile eels and a lone adult male Fiddler Crab were caught in a home-made trap called an ‘eel mop,”  a bucket of water with frayed rope to provide habitat for young eels to hide in.

After being photographed and counted, the eels were let go upstream in Lawrence Brook. From there, the little eels will swim upstream during the night at high tide stages and retreat to the bottom as tides fall during the day to rest. Glass eels will forge upstream with each tidal cycle and gain strength until they can swim against strong currents. Great fun to know all this natural activity is taking place about a mile or two away from New York City.

Sadly, though, the American Eel population seems to be diminishing in the northeast and even disappearing, worldwide, and no one really knows why. It’s difficult to protect a species when scientists know so little about it. Much more research needs to be done on American Eels to better understand their life cycle, and what they need to sustain their migrations. For example, while nearly all fishery scientists agree that adult American Eels migrate and spawn in the Sargasso Sea, hard evidence does not exist to show this activity in fact takes place. There is not one eye-witness account, picture, or video showing eels actually spawning in the Sargasso Sea. Remarkable in this day and age of so many things caught on film.

This is why baseline studies like those happening along Lawrence Brook in New Brunswick are so important. It helps to document that there are migratory fish actively using a waterway near New York City.

One of the best things we can do for eels is to allow scientists to study their life cycle. Another important activity is to open up and allow eels unrestricted access to waterways. Some waters around New York Harbor have small dams that may require a plan to address eel and fish passage. Another thing we can do is to make sure American Eels, especially glass eels, are not illegally harvested by commercial fishermen and local water quality is improved.

Although the American Eel may lack the beauty and charm of other migratory fish species, such as salmon, shad and striped bass, the American Eel is one of the most interesting fish in New York Harbor. If we work together, hopefully there will be countless baby glass eels waiting to be discovered and observed decades into the future.  

For more information, pictures and year-round sightings of wildlife in or near Sandy Hook Bay, Raritan Bay, and Lower New York Bay, please check out my blog entitled, Nature on the Edge of New York City at http://natureontheedgenyc.blogspot.com/