SHU Faculty and Students Work on Eel Tracking Project
For some, the idea of a silvery, two-foot long eel slicing through night-darkened waters while beaming a radio signal might seem best-suited for a science-fiction movie. For the partners in a project to tag and track American eels in the Aspetuck River, it’s an important idea that’s become a welcome reality.
Sacred Heart University Environmental Systems Analysis and Management Program graduate student Joe Cassone oversaw the transport of eels from Turner’s Falls and their release into the Aspetuck River. Cassone has been responsible for maintaining the radio receivers and managing the data they generate. He also has conducted tracking of the eels with a handheld receiver from the edge of the river and around the reservoir.
“Eels are doubly mysterious in that they camouflage well and migrate at night. In many cases, you can be in a stream or a lake and never know the eels were there. What was so exciting was being able to get hard evidence of what an eel was doing as it migrated out of the Aspetuck River system — to see when it tried to migrate and where it went. It was really satisfying to learn what was happening below the surface in middle of the night,” said Cassone
This fall, Aquarion Water Company, The Nature Conservancy, Sacred Heart University, the U.S. Geological Survey’s Silvio O. Conte Anadromous Fish Laboratory in Turner’s Falls, Mass., and the Connecticut Department of Energy and Environmental Protection (DEEP) have collaborated to release and monitor 30 radio-transmitter-tagged eels into the Aspetuck River in Easton.
The three releases, which included 10 eels each, were scheduled to coincide with significant rain events to spur the eels’ migrations, encouraging them to move downstream to salt water where they spawn.
Tracking of the eels ended around Dec. 1. A key goal was to gain valuable insight into how American eels — which have been proposed for federal endangered species listing — respond to river barriers and water diversions that create serious and sometimes fatal obstacles to the migrations that are crucial for the species’ survival. The partners anticipate continuing the tracking project next year.
“We’re proud of the strong partnership between The Nature Conservancy and Aquarion Water Company that has made this happen,” said John Herlihy, Aquarion’s director of water quality and environmental management. “The broader collaboration between a prestigious environmental organization, a water company, a university and federal and state agencies is a terrific example of what can happen when diverse organizations pull together around shared ideas and goals.”
As adults, American eels migrate downstream from their freshwater homes to the Sargasso Sea to spawn. The adults don’t return, but in the spring, juvenile eels will head for rivers like the Aspetuck to mature. They may remain in freshwater systems for 30 or 40 years before their biological clocks indicate it’s time to spawn, and they head back out to the Sargasso Sea.
“The problem for eels is they can have trouble finding safe passage downstream to salt water, especially in river systems with hydroelectric facilities or other diversions such as drinking water-supply systems,” said Sally Harold, The Nature Conservancy’s Connecticut director of migratory fish projects. “Through this incredible partnership, we hope to learn much more about how eels respond to weather events, temperature and light, so that we can develop strategies to direct the eel to safe downstream passage.”
The eel-tracking project is part of a multiyear collaboration between Aquarion and The Nature Conservancy. American eels that move into Aquarion’s Hemlock Reservoir — one of three interconnected Aquarion public water supply reservoirs in the Easton area — are at risk of perishing in the water plant there. Knowing eels avoid light, Aquarion and the Conservancy partnered in 2009 to install solar- and wind-powered lamps to route the eels away from the reservoir and toward a safer path.
The eel-tracking work that was started this year will provide valuable information about how eels are responding to underwater lights, river flows and conduit closures, such as between the Aspetuck and Hemlock reservoirs.
In addition to allowing the eels to be released and tracked from the company’s land, Aquarion paid for the surgically-implanted radio transmitters upon which the project relies. The company also agreed to shut its intake pipe to the Hemlock Reservoir for three days following each release to allow a better understanding of the lights’ effectiveness and behavior of the eel during “gate closed” conditions.
“This tracking study also will help Aquarion measure and document the extent of our success in enabling the eels to move downriver,” said Herlihy. “We need to know where we’re being effective and not effective to make the best possible decisions about additional investment to address these challenges.”
The eel-tracking project also relies on the expertise of Silvio O. Conte Anadromous Fish Laboratory, the Connecticut DEEP and Sacred Heart University.
The Conte lab loaned radio receivers for the project, and research ecologist Alex Haro has handled the delicate process of surgically fitting the eels with transmitters. The DEEP and supervising fisheries biologist Steve Gephard assisted in developing the project and planning for the green energy and lights installed in 2009. The agency has also helped with continued monitoring and project improvement.