It’s a warm, blue-sky Friday and I’m standing knee-deep in the clear, cold Fall Kill creek off the Hudson River in Poughkeepsie, New York. More than a dozen local high school and college students outfitted in rubber waders surround me. Two young men are helping to pull up a long, sock-like net, which corrals and traps baby eels. A group of girls shake out an “eel mop,” a large floating wooden disk with mop-like rope strands underneath that eels like to hide in, hoping the animals they’re trying to catch land in the bucket at their feet. Other students kneeling on a concrete platform on the shore are weighing and counting eels in large white buckets.

But the students aren’t just on a fun school excursion. They are so-called citizen- scientists performing important wildlife monitoring work that could lead to some potentially groundbreaking discoveries about a key ocean animal that humans are endangering yet know very little about: the American eel.

The students are part of the New York State Department of Environmental Conservation’s (DEC) Hudson River Eel Project. The program was established in 2008 as growing concerns over declines in eel catches led the Atlantic States Marine Fisheries Commission to mandate eel monitoring in states along the United States East Coast where eels migrate each spring from the Sargasso Sea.

“Eels are a historically abundant animal and important food source for all sorts of creatures, from fish to birds to other eels,” said Chris Bowser, program coordinator for the Hudson River Eel Project. “But in recent years, they’ve been overfished, sometimes to the point of extinction in some places like Japan, for human consumption.”

“In many places in the U.S., including the Hudson River region, dams and culverts block their migration upstream, killing many eels,” he added. “Fewer eels surviving in nature would mean a huge – probably devastating – loss of food” for birds, striped bass and other animals.

American eels are catadromous, meaning they are born in salt water and then migrate to freshwater to mature before returning to the ocean to reproduce and die. Baby eels serve as a food source for marine mammals, fish and birds. And they transfer energy from nutrient-rich ocean ecosystems to less productive freshwater environments, according to marine scientists.

American eel numbers continue to dwindle as fishers in the U.S. catch glass eels as they migrate into river mouths from the ocean. They then sell their catch for thousands of dollars a pound to aquaculture businesses in Asia that rear the eels and market the mature fish.

Despite eels’ high cost and declining numbers, they remain a favorite food source of people around the world, especially in Japan. Eel fishing in the U.S. is legal only in Maine and South Carolina, but poaching remains a significant concern.

Larry Pratt, a scientist at Woods Hole Oceanographic Institute who has studied American eel migration, said a lack of data about eels is hindering efforts to protect the species.

“How many glass eels show up in American rivers and creeks in a given year, when are they showing up, how much do those numbers vary from year to year, how do they know where to go from the sea when they get closer to freshwater, and how long do they live?” said Pratt. “Citizen science programs like the DEC’s could be very helpful in collecting large amounts of the long-term data needed to answer these questions.”

Bowser said “exponential increases” in the eel project’s participation rates in recent years have contributed to a greater local awareness and appreciation not only for eels, but the local Hudson River ecosystem as a whole – and even have global implications.

The fish being caught by the students are glass eels – a baby version of a full-grown American eel. I stand in the creek next to the two young men at the net, Marist College students Stephen Scalia, 23, and Robert Vahos, 22. Both tell me that an interest in pursuing a science education and career – as well as the prospect of spending time in nature – prompted them to volunteer.

Scalia and Vahos pull up the net from the water. Scalia digs a hand around in the gritty water inside. Suddenly he pulls his hand out and extends a tattoo-covered arm towards me. “Ready for an eel?” he asks. I nod. He opens his hand and in it rests a single glass eel: clear, wiggly and about the length of a large sewing needle. Full-grown eels reach nearly 60cm (2ft) in length.

“After hatching, these little guys come all the way to the Hudson from the Sargasso Sea, thousands of miles away,” said Scalia, as he gently lowers his hand into a bucket filled with water.

Scalia and Vahos are among at least 750 people – mostly students – who spent at least an hour once a week this past spring collecting data on the number, size and timing of the glass eels that migrate to the Hudson River region during “eel season,” which runs roughly six to eight weeks from March to May. The Hudson River region DEC recruits volunteers through word of mouth, at schools and at environmental fairs to work at one or more of their 14 monitoring sites.

After their required hour in the creek is up, the student volunteers return to shore and gather around Bowser for a final tally. Today was supposed to be their last day in the field for the season, but Bowser announced the students have collected 438 glass eels – an unusually high number for the season. He asks his “Friday eel crew” if they want to come back next week for one more day in the field to collect more data. The students shout a unanimous yes.

Bowser smiled, his blue eyes glinting with pride.

“When you think about it, it’s amazing we can get school kids excited to put on a pair of rubber pants and catch creatures that most people would turn their nose up at or worse,” said Bowser. “I think the eel is a secret weapon for citizen science. The eel goes on a journey, but when you choose to study eels, you go on a journey yourself.”