American shad — fish that migrate from oceans to rivers every spring to spawn — are making a comeback in New England’s longest coastal river without dams.

That’s the goal behind a new MassWidlife initiative which looks to stock about 2 million larval shad each year over the next five in the Taunton River, stretching 37 miles from Bridgewater to Fall River.

“They were once abundant in large Massachusetts rivers like the Taunton, but now only a small portion of their historical population remains,” MassWildlife said in a release this week. “Special techniques are needed to restore these migratory fish so that they become connected to a certain freshwater location.”

Shad are what wildlife biologists classify as diadromous, meaning they spend portions of their lives in both the ocean and freshwater rivers.

Newly born shad, still attached to their egg sacks, are being stocked in the Taunton River, allowing them to gain an “imprint on the unique characteristics of the river,” MassWildlife said. “This will aid in their navigation back to the Taunton when they return as adults after spending 3–5 years in the ocean.”

Shad, river herring and other diadromous fish swam abundantly in the waters of the Taunton River. That was before the Industrial Revolution, when pollution, overfishing and construction of dams made it impossible for the creatures to migrate to the river.

Monitoring shad populations in the Taunton River has been a focus for the state Division of Marine Fisheries and MassWildlife since 2017, and the stocking partnership with the federal Fish and Wildlife Service looks “to someday open the fishery to recreational harvest.”

“Today, water quality improvements and an increase in habitat quality and quantity through dam removal have allowed for the opportunity to bring back this historically important fishery,” MassWildlife said.