This commentary is by David L. Deen of Westminster, a member of the Vermont Fish and Wildlife Board and the Connecticut Atlantic Salmon River Commission. He writes about, lectures on, and fishes the Connecticut River whenever he can.
The American eel (Anguilla rostrata) is a peculiar fish and not just because it can survive out of water for several hours, breathing through their skin.
Their migration cycle is contrary to other migrating fish in the Connecticut River. They come into the river as juveniles, leave as adults, and most sources claim they spawn in the Sargasso Sea. That makes them the only fish in our watershed to migrate to the ocean as adults.
The American eel is not a lovable creature. Adults are 3 to 4 feet long. Despite one long dorsal fin that extends more than half of their body length and two smaller pectoral fins, they look and move like snakes. They are muscular, with a girth the size of your forearm and their body slime does make them “slippery as an eel.”
They are a top predator in our river and they will bite anything that annoys them, including anyone who inadvertently hooks one while fishing. If they cannot swallow a meal whole, they bite into their prey with their array of teeth, spin their bodies, and tea pieces from their quarry. They do not even benefit from a cute factor, because the juveniles are less than 4 inches long, are close to transparent, and travel at night.
The eel is an ancient fish, having lived on earth for 100 million years, outlasting most of their contemporary species. Females live in fresh water for up to 20 or so years before returning to the sea, where the female lays up to 20 million buoyant eggs. Once fertilized, the eggs hatch within a week, becoming transparent leptocephalus larva that drift toward coastal waters for up to 18 months. At sea, they consume plankton, insects, and floating dead tissue.
As they cross the continental shelf (75 to 200 miles offshore), the larva transform into glass eels that are still transparent but now have the elongated eel shape. Upon reaching mixed salt and fresh waters (estuaries), they morph into elvers and enter our river at 1 to 4 inches in length and still nearly transparent.
As elvers, they become carnivores, voracious feeders, and aggressive swimmers. They are most active at night.
The elves have never been in the Connecticut River before, so one has to wonder how they select the Connecticut as their returning river. The fish do have a small spot of magnetite in their heads, so they sense magnetic direction, but no one knows if this directs the eel to a particular river.
In the elver phase, the sex of the eel is still undetermined. The elver stage lasts up to 12 months and all the while becoming adults, they are busy migrating upriver.
Once upriver, they transform into sexually immature yellow eels. As they begin to develop their yellow/brown color, they identify their sex. Species density influences sexual differentiation and a high density of eels in a particular reach of river will cause there to be more males.
In eight to 20 years or so, they will become silver eels and spawning time has come. Like all fish that migrate to the ocean, their change is more profound than color. Internal changes prepare our eels to migrate back to the salt of the sea — the digestive tract shrinks, the pectoral fins enlarge to increase swimming capacity, the skin thickens, body fluids make changes, their swim bladder increases in size, eye diameter expands, their retinas adapt to ocean colors, and internal egg or sperm production begins.
The eel was once the most common finfish in the Connecticut River watershed. Be they lovable or not, protection and restoration of eels in our watershed is an ongoing concern for the Federal Energy Regulatory Commission relicensing of the mainstem hydroelectric dams and those sprinkled throughout our tributaries.
In recent river history, we have invested heavily in passage for migratory fish, salmon, shad, lampreys, and blue-backed herring, but none of the passage methods work well for eels.
Continued blockage of migrating eels up the mainstem and the tributaries could mean the failure of eels as a species in our watershed, even though we know how to successfully pass eels over dams and the costs to do so are minimal. Think of a sliding board with indoor/outdoor carpeting on its surface stretching from below a dam to above the dam with water trickling down the carpeting and voila, you have eel passage. Elvers moving upriver are determined wigglers and up is all they know or want.
One can only hope that FERC will require eel passage in the new licenses for Connecticut River watershed power stations. That will be an important step in maintaining our peculiar fish throughout their traditional habitat from Long Island Sound to the Connecticut Lakes.
