CONTACT: Michael Globetti, DNREC Public Affairs, 302-739-9902
“Glass eels” counting themselves in for abundance
in Delaware Estuary, new DNREC YouTube video shows
DOVER (March 4, 2016) – The American eel would seem one of the slipperiest species to get a population handle on, but a new DNREC YouTube Channel video shows otherwise – with Division of Fish & Wildlife biologists conducting a survey of young “glass eels” tallied thousands at a time by “enumerating them volumetrically” with a device known as a splitter box.
On a single splitter capture, as DNREC’s YouTube Channel documented the effort, more than 7,000 eels were counted – which fisheries biologist Jordan Zimmerman said indicated a good abundance of American eels in the Delaware Estuary (a survey day earlier this year turned up 65,000 glass eels, while another day’s count in a recent year reached almost 100,000).
The glass eel count program was established as a fisheries management plan tool for monitoring reproduction in the American eel. “Glass eels” are another stage of the American eel’s life cycle, first stage being the egg, which hatches into larvae drifting on the Gulf Stream and eventually metamorphosing to the glass eel stage and swimming toward shore and the estuaries. “The glass eel gets its name because it’s fairly translucent. Once it reaches fresh water, it will start to get pigment, and will eventually become what's known as a yellow eel,” says Zimmerman.
Eels in Delaware remain in the yellow phase from six to 10 years, when they metamorphose again into the silver eel phase. “They essentially cease eating at that point…for the long migration back to the Sargasso Sea and the Caribbean” – to spawn once before they die, and start the eel migration cycle back to Delaware waters.
“Eels play both a valuable ecological and economical role in Delaware,” Zimmerman says in the video, “typically averaging out to be the third largest finfishery here in terms of their economic value. Ecologically, they are prey for numerous species of birds, fish, turtles, etc.”
On the DNREC YouTube Channel video Zimmerman is convinced by this year’s glass eel survey that “Things are looking up for the abundance of American eel, and the persistence of the species, and its (continued) importance in the Delaware Estuary.”
Vol. 46, No. 67