While the unusual early return of blueback herring and alewives to the coastal rivers and streams is making news this month, there’s another aquatic migrant that deserves our attention—one whose journey from sea to freshwater and back is no less remarkable than that of the aforementioned river herring.
I’m talking about elvers, also known as glass eels. Elvers are juvenile American eels, and they enter the coastal waterways from Texas to Nova Scotia each spring after developing from eggs and then larvae carried by currents from the species’ spawning grounds in the Sargasso Sea. They are “catadromous” fish, spawning in saltwater and spending most of their lives in freshwater (although some eels remain in salt or brackish waters after arriving at the coast).
Meet the Elvers
I had never seen elvers in the flesh until I was checking out a local herring run in late March and I noticed some in the freshwater pond above dam. Maybe I had never really looked for them, but the more I looked, the more elvers I saw. Every minute or so, one of the 3”-long, flagellate-like animals would wriggle through in the tea-colored water, occasionally scooting in to hide among the mossy vegetation that grew on the rocks.
I returned the next day, intent on capturing a few of the critters with a dipnet. This proved difficult, however, as elvers turn out to be very fast and very slippery. This should come as no surprise to anyone familiar with adult American eels—perhaps the slimiest creatures on earth next to hagfish.
Plenty of Predators
The baby eels need to be even more elusive, since almost everything eats them, from herons to trout. Humans too. Glass eels—so-called for their transparent bodies—command a huge price in Asia, where they are grown to maturity and sold as a delicacy. The high price of eels spawned a gold-rush fishery that eventually led to limits on their harvest in the U.S. Poaching remains a problem in some areas, as a pound of elvers can fetch up to $2,200.
Aside from a gauntlet of predators, elvers must also contend with fish ladders and dams during their odyssey from the ocean to the freshwater rivers, ponds and lakes where most will mature. For whatever reason, a number of eels choose to remain in brackish and tidal areas along the coast, where they feast on a variety of detritus, and provide a source of food for striped bass and birds. Once the eels reach maturity—they can grow up to 4’ long and a weight of 9 pounds—they return to the ocean and make their way back to the Sargasso Sea, where they die after spawning.
Threatened Listing Looms
Whether due to overfishing, habitat destruction, disease, increased predation, a naturally occurring cycle or some combination of factors, the coastwide population of eels in the U.S. has declined alarmingly in the last decade, prompting the federal government to consider listing the species as threatened. Such a listing would make eels off-limits to harvest, both for food and for sale as bait. The US Fish & Wildlife Service is still considering the most recent petition to list eels as threatened.
Knowing all of this, I was excited to see so many elvers in my local waters, and desired to know them better. After several unsuccessful attempts at netting the individual eels that happened to swim with range, I played a hunch and used my net to scoop up some of the aquatic plants at my feet. Eureeka! I hit the jackpot, as several elvers immediately wriggled out of the mossy vegetation, where they had been hiding. I placed them in a jar and observed them for a bit then returned them to the pond. After all, they’d been through quite enough already.