We Want to Know More About Eels in Lake Champlain

The depths of Lake Champlain are home to some of its most intriguing species, including freshwater eels. Eels may have a reputation as a slimy fish slithering around under your feet, but there’s much more to their elusive life than meets the eye. Eels migrate thousands of miles from their spawning location in the Sargasso Sea to inland rivers and lakes like Lake Champlain to grow before heading back to sea to spawn just once in their lives. These fish once made up a quarter of the biomass in some New England streams but today, their population is struggling.

A new study led by researchers at the University of Vermont dives deep into Lake Champlain to figure out where eels are living, how they’re getting around, and how barriers like dams affect their distribution. With help from multiple agencies and decades of fish surveys dating back to the 1920s, the team pieced together a giant database of eel sightings.

“There’s so much we don’t know about eels,” said lead author Rose Stuart. “They’re out there, but because eels have been largely overlooked, we’ve had to piece together a patchwork of past data to see the full picture.”

Eels are still present throughout Lake Champlain and its tributaries. They’ve been found at depths of nearly 300 feet in the lake, and up to 40 kilometers up tributaries. In many cases, they’ve climbed past small dams to reach these areas, being commonly found upstream of dams under 3 meters tall.

But bigger dams still pose major barriers. In fact, eel sightings drop dramatically in areas with multiple dams in a row. While young eels can be good climbers, the larger individuals reaching Lake Champlain often can’t make the same journey. This restricts their access to habitat and may crowd them downstream where disease and competition rise.

Between 2005 and 2010, an experimental conservation program operated by Faune Quebec and HydroQuebec stocked 2.7 million baby eels (called “glass eels”) into the upper reach of Quebec’s Richelieu River, which connects the St. Lawrence River to Lake Champlain. Because of their small size and good climbing ability, these stocked eels were able to reach areas where barriers restrict the naturally migrating eels such as Lake Bomoseen and the Lamoille River. This poses some questions about the viability of these stocked fish. Will they be able to move back downstream with the same ease they migrated upstream as glass eels? Can these transplanted fish survive the journey back to the sea? And will they successfully reproduce?

Better data is needed, especially in Vermont’s tributaries, to know where eels are thriving or struggling. The research suggests creative solutions, like adding eel ladders to more dams or designing ways to help eels move both up- and downstream safely. The findings also emphasize the cumulative effects multiple dams, even small dams, have on eel migration. To complicate eel management further, the same dams that block eels are also used to manage invasive sea lamprey, a fish that harms native fish like salmon.

The researchers urge more surveying of eels, specifically in the Vermont section of the basin to map distribution and the presence of eels above and below dams. They also suggest standardizing methods of surveying, noting previous studies have used many different techniques that may yield different data.

“Eels are remarkable,” said Stuart. “And if we want to keep them around, we need to understand the basics of how they are using this habitat, and the challenges they may be experiencing.”

Right now, Quebec is planning is to reestablish glass eel stocking in Lake Champlain. This makes surveying eels even more critical. Stuart et al. suggests surveying before any stocking takes place. Regardless of stocking efforts, the researchers say that more frequent surveying will help us understand where eels live and how they navigate our human-modified rivers which can guide smarter decisions as Vermont and its neighbors look to restore this ancient, slippery species.