Waiting for Slimy Signs of Spring

Aug 29, 2023

Photos by Chris Bowser, NYSDEC/HRNERR.

The American eel is soooo misunderstood. It’s not electric, dangerous, or nearly as slimy as people think—and what’s wrong with slime anyway? Nothing, according to the thousands of volunteers who have supported the Hudson River Eel Project, which is co-led by the Hudson River Reserve. Over the last decade, their willingness to wade into the Hudson’s chilly spring waters and count eels has generated a body of data so useful the Atlantic Marine Fisheries Commission is including it in their upcoming benchmark status report on juvenile eels, supporting eel management along the Atlantic Seaboard.

“These eels have had a tough century,” says Chris Bowser, education coordinator at the Hudson River Reserve. “They are characterized as a “depleted species” throughout their range on the Atlantic coast. To better protect and manage them we need a lot of data and that’s weather our local community scientists have played an essential role.”

Every spring, about a thousand volunteers jump into their waders to check special nets in the Hudson and tributary streams for “glass eels,” the juvenile stage of the American eel that migrates into estuaries each spring. They count the transparent baby eels they find and then respectfully return them to the river, usually above a dam or barrier so they can continue with their miraculous migration from the Sargasso Sea to freshwater streams. 

It all sounds straightforward, but timing is everything! Research has shown that glass eels entering estuaries may have a “gateway” threshold of around 50 degrees F. Once the river temperatures get to about that level, other factors determine the rise and fall of eel numbers, but in-water temperature seems to be the key factor to cue their entrance.

“It’s tough to predict the eel migration,” says Chris Bowser, education coordinator at the Reserve. “We want to capture the start of the migration, but if we ask volunteers to keep checking empty nets in cold streams for weeks on end, we’ll have a lot of frustrated ex-volunteers!”

Bowser and his colleague Sarah Mount, science educator at the Reserve, use local data from the Hudson River Environmental Conditions Observing System (HRECOS) to carefully watch the water temperature day by day. “When we see the river climb into the low 40’s, we ask some of our down-river partners to start looking,” says Mount. “First they use some artificial habitat traps called eel mops, and once we see our first brave eels, it’s net time.” 

Through HRECOS, the Reserve shares the place-based data they collect through its chapter of the the NERRS System-wide Monitoring Program to maximize the efficiency of their eel monitoring effort, while also making the project doable for the volunteers that make the project possible. 

“Partnership is key to almost everything we do,” observes Bowser. “The Eel Project would never happen without the collaboration of many groups.” That partnership has extended to working with the Atlantic States Marine Fisheries Commission, which oversees juvenile eel monitoring from Florida to Maine. “We keep in close touch with the ASMFC,” explains Bowser, “and follow their suggestions to make our data robust and in the larger context of eel conservation.”

The New York project slipped over the border to New Jersey, where the Jacques Cousteau Research Reserve in New Jersey has also started a community science effort to monitor eels, thanks to a NOAA and NERRS Science Collaborative Grant.

Want more Reserve stories delivered to your inbox? Subscribe to our newsletter.

ReservesHudson River, New YorkWaiting for Slimy Signs of Spring