The American eel (Anguila rostrata) is so misunderstood. It’s not electric, dangerous, or nearly as slimy as people think—and what’s wrong with slime anyway?
These eels have had a tough century; the Atlantic Marine Fisheries Commission (ASMFC) lists them as a “depleted species” throughout their range. Community-science data contributes to the ASMFC’s status reports. Each spring a thousand volunteers from the Hudson River Eel Project jump into their waders to check special nets for “glass eels”, the juvenile stage of the American eel that migrates into estuaries each spring. The volunteers check their site’s net each day and count the transparent baby eels, Then the eels are respectfully returned to the river, usually above a dam or barrier so they can continue with their miraculous migration form saltwater 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.
That’s where HRECOS comes in. “Its tough to predict the eel migration” says Chris Bowser, education coordinator of the Hudson River National Estuarine Research 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!”
So Bowser and his colleague Sarah Mount use 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, its net time.”
“The scientist in me loves to see a few days of zero catches at the start of the season,” says Bowser, “but soon after, its good to see the eels start showing up.” HRECOS allows Bowser and Sarah to maximize the efficiency of their eel monitoring effort, while also making the project doable for the volunteers that make the project possible.
You can learn more about the Hudson River Eel Project here: https://hrnerr.org/eel-monitoring/
In the last few years, The Jacques Cousteau Research Reserve in New Jersey has also started a community science effort to monitor eels: https://hrnerr.org/eel-monitoring-ny-nj/
And if you like podcasts, check out “But Why?”: https://hrnerr.org/but-why-eels/