FREETOWN – River herring and American eel will return next spring to Rattlesnake Brook in Assonet for the first time since the mid-1800s, following the demolition of the former Crystal Springs Bleachery Dam, environmentalists said Friday.

The 400-foot long by 30-foot wide, earthen and stone dam was demolished shortly after work started Oct. 21 as part of a $600,000 public-private sector project to improve public safety, restore a passageway for fish and return the area to its natural state.

“This reconnects Rattlesnake Brook with the Taunton River,” said Alison Bowden, the freshwater program director for The Nature Conservancy. The brook is part of the Taunton River Watershed, which has received the federal designation as a Wild and Scenic River.