BOSTON — A sighting of an Atlantic sturgeon in the Charles River Locks is delighting aquatic specialists who say the ancient fish is fighting for its survival.

The Boston Globe reports that the fish was photographed by a bystander and confirmed by an official at the state’s fisheries and wildlife division.

Julie Wood, watershed scientist at the Charles River Watershed Association, says the sighting of the sharp-snouted fish, which predates dinosaurs, is good news. Federal officials recently listed Atlantic sturgeon as endangered in five areas along the Atlantic and as threatened in the Gulf of Maine.

Sturgeon were abundant in Colonial times, but overfishing and limited access to freshwater spawning areas reduced their numbers.

The watershed association says pollution of the Charles peaked in the last century, but decades of work have cleaned it up.