That opens the door to federal disaster assistance to the industry.
The announcement by Commerce Secretary Carlos Gutierrez comes in response to a request two months ago by Massachusetts Gov. Duval Patrick.
Shellfish closures arising from the toxic algae bloom began in May, in waters off Massachusetts and spread north to New Hampshire and Maine. The closings bar the harvest of clams, mussels, oysters and other shellfish where red tide has been detected.
Officials say some closings have been lifted, but many areas still remain off-limits to harvesting.