N.H. Rev. Stat. Ann. § 211:63-b

The executive director, after a public hearing, may order a closing of clam, oyster, and other bivalve areas for the purpose of restoration of the area, provided that the closure will not unduly interfere with existing or anticipated commercial or recreational activities. When such closing for restoration is ordered, the order shall be effective immediately without a waiting period and shall continue in effect for a period of not more than 5 years. No more than 50 acres shall be closed at any time.