Vermont, September 2013. The American eel (Anguilla rostrata) is a peculiar fish and not just because they 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 catadromous fish in our watershed.
The American eel is not a loveable creature. Adults are 3-4 feet long. Despite one long dorsal fin that extends more than half of the body and two smaller pectoral fins; they look and move like snakes. They are muscular with a girth of 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. If they cannot swallow a meal whole, they bite into their prey with their array of teeth, spin their bodies tearing pieces from their quarry. They do not even benefit from a cute factor, because no one sees the juveniles as they 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 freshwater for up to 40 years before returning to the sea. The 80 species of eel worldwide are scattered in the Americas, Europe, the Pacific Rim and the Caribbean. For these other locales, the spawning grounds are in different oceans around the world. Sources say no one has ever witnessed American or any other species of eel spawn but spawn they do and the ensuing life stage changes into adulthood are remarkable.
The female lays up to 20 million buoyant eggs and 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, leptocephali metamorphose into glass eels that are still transparent but now have the elongated eel shape.
Upon reaching estuary waters, they change into elvers and enter our river as elvers, 1 – 4 inches long and still nearly transparent. As elvers, they become avid carnivores. In fact, eels beyond the leptocephalus life stage are voracious feeders, aggressive swimmers and are primarily active at night.
As the adults of other migrating fish are swimming up river to spawn, the juvenile eels swim up river to grow into adults. They have never been in the Connecticut River before so one has to wonder how they select the Connecticut as their returning river. The fish does have a small spot of magnetite in its head 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 twelve months and while becoming adults, they are busy migrating up river.
Once up river, 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, the higher the density of eels the more males.
In 20 to 40 years, they become silver eels and spawning time has come. Like all fish that migrate to the ocean, the change is more profound than color. Internal changes prepare our eels to migrate back to the sea as the digestive tract shrinks, the pectoral fins enlarge to increase swimming capacity, the skin thickens, body fluid make up changes, their swim bladder increases in size, eye diameter expands, their retinas adapt to ocean colors and egg or sperm production begins.
Worldwide people have considered the eel a tasty fish for thousands of years. The largest consuming nation is Japan where they even make a “unagi inu,” grilled eel placed on a bread bun, their equivalent of our hot dog. The fishery for glass eels and elvers is huge in the two east coast states that allow it, fetching $2,500.00 per pound. Part of the glass eel catch supports eel farming now underway in Japan and China. Yet, in a situation where the species cannot win for losing, major consuming nations still prefer wild eel so the fishing pressure in the wild remains strong.
Once the most common finfish in the Connecticut River and be they loveable or not, protection and restoration of eels in our watershed is a CRWC concern in the ongoing FERC relicensing of the mainstem hydroelectric dams. 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 works 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. If the CRWC call for effective eel passage is successful, we hope to increase the numbers and distribution of the peculiar fish of the Connecticut River, the American eel.
David L. Deen is River Steward for the Connecticut River Watershed Council. CRWC is celebrating 60 years as a protector of the Connecticut River.