New London — An Atlantic sturgeon, a federally endangered species not found in the Thames River since the 1980s, has been detected using the area of the river adjacent to the Naval Submarine Base in Groton, potentially affecting the plans to demolish two piers, dredge the waterfront and build a wider, longer pier.

Tracey McKenzie, natural resource manager for the sub base, shared that information Friday during a presentation to about 30 people in the Thames River Basin Partnership at the New London Maritime Society.

Members of the partnership, comprising representatives of two dozen local and state government agencies and nonprofit conservation groups in the Thames River watershed, gathered for the group’s annual workshop.

McKenzie said the fish, an ancient species that can grow up to 14 feet long, was detected four times by receivers placed in the waters off the sub base that capture signals from transmitters implanted in sturgeon as part of projects by various academic researchers.

Based on this finding, she said, the Navy is planning to install more receivers at the mouth of the Thames and other locations in the river to determine how frequently sturgeon, which move from salt water to fresh water or up rivers to spawn, use the area.

“We’re trying to determine if this is a fluke or an anomaly, or do we have sturgeon using the river,” she said. “It’s possible sturgeon are using the river as a foraging place.”

Tom Savoy, fisheries biologist with the state Department of Energy and Environmental Protection, said Atlantic sturgeon from other states swim into Long Island Sound from May to October.

There is also a small population of Atlantic sturgeon spawning in the Connecticut River.

“But predominantly, these are fish from other areas that use Connecticut waters in the summer as important feeding areas,” Savoy said.

The fish found by the sub base, he said, was a “sub adult” about 2 to 3 feet long.

He said DEEP is encouraging the Navy to install a network of receivers in the Thames River to collect more information — not just on sturgeon, but on other species as well.

“We’ll be able to get more information on a variety of species,” he said. “We’re encouraging that in return for them getting the permits to do their construction and dredging work.”

The Navy also has notified the National Marine Fisheries Service about the sturgeon, McKenzie said.

Under the Endangered Species Act, the Navy would be prohibited from any activities that could harm the sturgeon, if they are found to be using the area regularly.

Savoy said Atlantic sturgeon were declared an endangered species in 2012.

“This is a species that really needed the protection,” he said. “They could go extinct in our lifetime. They’ve been on the planet for 60 to 100 million years, but in the last few centuries they were heavily fished, and they lost access to their spawning areas when the rivers were dammed.”

McKenzie said the Navy conducted surveys of waters from the shore of the base to 820 feet into the river in 2015, collecting data during each of the four seasons.

The work was done in preparation for the planned demolition of Piers 32 and 10, dredging of that area and rebuilding of a longer, wider Pier 32 to accommodate the Virginia-class submarines.

The demolition work is tentatively slated to take place in 2019, McKenzie said.

Along with the sturgeon, the surveys also found 30 other species of fish using the area, including three that use it as “essential fish habitat.”

Windowpane flounder were found using the area, from egg-laying to hatching to juvenile to adult stages of life, while bluefish and Atlantic herring use it in juvenile and adult stages, she said.

The marine fisheries service will require that the project minimize disruption to these species, McKenzie said.

“It’s important to know what fish species we have at the sub base, so that when we’re doing construction projects, we’re not doing damage to essential fish habitat,” she said.

j.benson@theday.com