In this May 25, 2017 file photo, hundreds of baby eels, known as glass eels or elvers, swim in a bucket after being caught on the Penobscot River in Brewer, Maine. Despite the ongoing effects of the global COVID-19 pandemic, and concerns about eel populations around the world, demand for glass eels caught in Maine this year is expected to be higher than in 2020. Credit: Robert F. Bukaty / AP

Each spring, when great masses of baby eels swim from the sea up rivers and streams in Maine toward freshwater, roughly 24 million of the small, clear and spaghetti-like creatures are caught in nets, sold and shipped off to supply the world seafood market, mainly as unagi on sushi menus.

Beyond that, not much is known about American eels in Maine or elsewhere along western shores of the Atlantic Ocean, except that Maine’s annual springtime baby eel fishery is collectively worth about $17 million to the hundreds of Mainers who catch them.

Eels — which spawn at sea each spring before swimming into freshwater watersheds where they live for years before swimming back out to sea to reproduce and die — are considered one of the world’s most enigmatic fish.

The smallest larval eels scientists can find are in the Sargasso Sea, out in the middle of the North Atlantic Ocean, but no one has ever seen adult eels reproducing. Nor has anyone ever been able to get eels to reproduce in captivity. Sigmund Freud, before he became known as the founder of modern psychoanalysis, once famously spent a summer as a student dissecting eels in Trieste, Italy, searching for their reproductive organs — before it was determined that eels don’t develop these organs until late in life, not long before they return to sea to procreate.

The mysterious nature of eels, which are active at night and dormant during the day, has been perplexing for fisheries regulators who aim to protect them from overfishing or habitat degradation caused by dams and pollution. Overfishing of eel species anguilla japonica in East Asia, and of the anguilla anguilla eel species in Europe — and tight fishing restrictions imposed for those species — have increased demand for anguilla rostrata, the American eel found in Maine.

In turn, the value of Maine’s annual harvest for baby or glass eels — also called elvers — has ballooned from a few hundred thousand dollars each year into a multimillion-dollar enterprise. The annual glass eel fishing season in Maine typically starts in late March and runs to early June.

It was 10 years ago this month, when an earthquake and tsunami struck Japan, that the availability of farmed eels in that country plummeted, boosting the price of glass eels in Maine. A ban on exports of glass eels from Europe in December 2010 also heightened demand for Maine eels the next spring, causing the average price earned by Maine fishermen to skyrocket from $185 in 2010 to nearly $900 the following year, and then to more than $1,800 in 2012.

In the years since, the Atlantic States Marine Fisheries Commission has imposed an annual statewide catch limit of 9,688 pounds (with each pound averaging roughly 2,500 glass eels), and the annual average price paid to Maine fishermen has balanced out over those 10 years at more than $1,500 per pound — swinging as high as $2,366 in 2018 before falling back to $525 last year, when the onset of the global COVID pandemic greatly suppressed international trade.

Lack of data

Despite the abundance of data about the impact of eel fishing on Maine’s economy, not much is known collectively about eels that don’t wind up in fishermen’s nets.

Gail Wippelhauser, a Maine Department of Marine Resources scientist, has been to the Sargasso Sea searching for answers about the life cycle of eels. There is little to no data about the population of eels in the Caribbean, Central America, South America, the Gulf of Mexico or the Mississippi watershed, she said.

Most of what is known about the American eel population, which still isn’t much, comes from the East Coast, where tens of thousands of adult eels, each weighing roughly 10 pounds or more, are harvested in several states, Wippelhauser said. In the late 1970s and early 1980s, more than 2 million pounds of eels were routinely harvested each year along the East Coast. More recently, she said, the total annual harvest from Florida to Maine has ranged from 700,000 to 800,000 pounds.

Maine and South Carolina are the only states that allow fishing for glass eels, and the yield in South Carolina, where only a dozen or so fishermen are licensed, is much smaller than in Maine. The vast majority of glass eels caught in the U.S. are shipped live to Asia, where most are raised to adult stage in aquaculture ponds in China, then shipped to Japan and other countries.

“We don’t even have good information for Maine,” Wippelhauser said, even though far more eels — albeit tiny ones — are caught in Maine than anywhere else in the United States. There is no approximate scientific consensus for how many adult eels might live in Maine’s rivers, lakes and ponds.

While the Atlantic States Marine Fisheries Commission decided in 2012 that the population of American eels was depleted, the lack of significant data about the population is why the U.S. Fish and Wildlife Service decided three years later not to list the species as endangered. To have been listed, federal regulators would have needed ample evidence that eels’ population was being hurt by specific factors.

“For listing, there are certain things you need to demonstrate,” Wippelhauser said. “If there was a big uncontrolled glass eel fishery in every state, I would be concerned about that.”

Because American eels have such a broad geographic range — from northern South America up to Canada — it’s hard to determine how big of an effect a single factor, such as a particular predator or a single state’s eel harvest, has on their population, she said.

Eel population impacts

Maine conducts ongoing sampling of eels it catches at West Harbor Pond in Boothbay Harbor. It counts glass eels there every spring and, in the past couple of years, has also caught and counted yellow eels (adults that are not yet sexually mature) and silver eels (sexually mature eels that are on the verge of migrating back out to sea to reproduce).

Department of Marine Resources researchers have caught high numbers of glass eels in the pond, which is a saltwater inlet, in the past few years, but also have found that between 40 and 85 percent of adult eels have a parasite in their swim bladders, which affects their buoyancy in the water, Wippelhauser said. Eels are bottom dwellers, so the parasite is not believed to be an issue for them when they are in lakes and rivers, she said, but it may well be a problem when they swim back out to sea, where sinking to the ocean floor would prevent them from spawning in the Sargasso Sea.

Another factor that affects eels — though now to a lesser extent after some have been removed in recent years — is the presence of dams. Wippelhauser said dams that have taller and/or faster turbines are more likely to injure eels as they move downstream. Female silver eels, which tend to be relatively big, are more likely to be injured than males, which tend to be smaller.

The impact of climate change is harder to determine, she said. With their range extending from tropical waters to Canada, temperature does not appear to affect the eel population. Scientists do not know if heavier rainfall events, which could make the upstream springtime migration of glass eels more arduous, or drought, which reduces water levels, might have a greater impact.

However, there is some indication that climate change could slow down the Gulf Stream, which is a current of warm water that runs north along the East Coast from Florida past Newfoundland in Canada. Eel larvae and glass eels are not strong swimmers, she said, and are believed to rely on ocean currents to randomly deposit them at freshwater outlets along the shore.

“If that were the case,” Wippelhauser said of a potentially slower Gulf Stream, “that might inhibit their distribution.”

Commercial distribution of Maine-caught glass eels to Asia is an easier thing to anticipate, even when unexpected earthquakes and disease pandemics strike.

Mitchell Feigenbaum, a seafood distributor who ships glass eels from the East Coast to Asia, said global demand for young eels is expected to be higher this spring than it was a year ago. The supply of eels from other parts of the globe, including those smuggled illegally out of Europe, currently is low, and the economic damage of the COVID-19 pandemic is abating.

But the Asian seafood market still has yet to fully recover, Feigenbaum said. China still has restrictions in place on banquets and other large gatherings, while in Japan the lingering disease still is hampering the restaurant business. Plus, with the lack of demand last year, there is expected to be an ample supply this year of adult-farmed eels, all of which is expected to limit how much prices rise.

“Prices should be much improved over last year, but far below where they were in 2019,” he said.

Bill Trotter

A news reporter in coastal Maine for more than 20 years, Bill Trotter writes about how the Atlantic Ocean and the state's iconic coastline help to shape the lives of coastal Maine residents and visitors....