Delaware Dam Becomes Eel-Friendly

Published March 1, 2009

Migrating American eels will find it much easier to reach freshwater habitats in coming years thanks to a new eelway being installed at a key Delaware dam.

The eelway, coming to the Millsboro Dam at a cost of $2,000, eases the first and most imposing chokepoint along one of the nation’s most important eel migration routes.

Long Migration

American eels migrate more than 1,000 miles from salt water to fresh water, beginning in the Sargasso Sea in the Atlantic Ocean. Their migration begins soon after birth, when they make the long trek to bodies of fresh water, where they mature. Thereafter, they return to the ocean to spawn.

The American eel is of special concern because low numbers make it a candidate for the federal endangered species list.

The Atlantic States Marine Fisheries Commission is requiring states to monitor eel populations to help the commission implement an effective management plan. The new eelway will help increase the eel population, allowing eels to take up residence in upstream lakes, streams, and ponds that were rendered off limits by the Millsboro Dam.

Simple Assistance

The new eelway looks much like a rooftop rain gutter. Inside, bumpy pegs allow the eels to climb the dam with relative ease.

Eels typically use natural fish ladders to get around such obstacles, according to Sara Grady, watershed ecologist at the North and South Rivers Watershed Association in Norwell, Massachusetts.

“In the United States, the technology that’s used to help pass eels is to build a ramp that has a rough surface that the eels can use to grip onto. They are pretty good at climbing surfaces that don’t even have a lot of water, but they do require something that has some friction, so some [eelways] are built with almost an Astroturf material, and others are built with a series of small pegs,” said Grady.

No Negative Consequences

“Fish like herring and chad need a different kind of ladder than fish like eels,” Grady added. “They migrate in opposite directions. Essentially a ladder built for eels would not necessarily help all migratory fish. If it wouldn’t cause any problems, usually any sort of fish passage structure is a benefit. Anything that helps fish pass obstructions, I would consider to be a good thing.”

“Fish ladders are a well-established concept, and a lot of times they can be geared towards the needs of specific species,” said Paula Rees, director of the Water Resources Research Center at the University of Massachusetts Environmental Institute.

“In this case, it doesn’t sound like it would be dangerous,” Rees said. “Fish ladders in general are very good. If we didn’t have fish ladders in the western United States, we wouldn’t have any salmon. The same thing is happening with fish migration in the northeastern United States, [as in] Maine.”

Krystle Russin ([email protected]) writes from Texas.