PORTLAND — The National Oceanic and Atmospheric Administration says it will focus conservation efforts on the Penobscot River watershed area in Maine and the Choptank River complex in Maryland and Delaware.

The agency announced Monday that the two waterways have been designated “Habitat Focus Areas.”

The Penobscot is New England’s second largest river and serves as a habitat for three endangered fish species, the Atlantic salmon, Atlantic sturgeon and shortnose sturgeon.

The Choptank is the largest river on the Delmarva Peninsula. Its Eastern oyster population has been reduced to 1 percent of its historic levels.