A fisherman accidentally netted three endangered shortnose sturgeon, a species rarely seen in the Chesapeake, near Aberdeen, Md., on April 2. Two of the fish weighed 3 pounds each while a third weighed 6 pounds. The fish ranging from 27 to 32 inches in length, were released into Little Northeast Creek after they were identified by U.S. Fish and Wildlife Service biologists.

Shortnose sturgeon have been listed as a federally endangered species since 1967. Overfishing, damming of rivers and degraded water quality are the primary causes of their decline.

Several scientists indicated that, given where the fish were captured, they probably were not native to the Chesapeake, but most likely entered the Bay through the Chesapeake and Delaware Canal. Shortnose sturgeon are more common in the Delaware River.

"There are some indications these fish move out once the population reaches a certain size, and it could be that the population in the Delaware River has gotten so big, they moved over at some point," said Jorgen Skjeveland, a USF&WS biologist with the agency's Maryland Fisheries Resource Office in Annapolis.

Skjeveland said no one knows whether the shortnose were ever abundant in the Bay because old fisheries records do not indicate what kind of sturgeon were being caught. "Just sturgeon, period, is all they ever put down," he said. "No one ever differentiated back when they had the big fishery, so who knows?"

Shortnose sturgeon are an unusual-looking fish. Instead of scales, both the head and body of the sturgeon are covered with bony plates, resembling armor. Shortnose sturgeon occur in large rivers and estuaries along the Atlantic Coast.

They spawn in upper, freshwater portions of rivers during the spring, migrate to the mouths of rivers in summer and fall, then move into deeper, slightly saltier environments for the winter. Shortnose sturgeon can live for 50-60 years. In the mid-Atlantic, females mature at 6-7 years, while males mature at about 3-5 years.