PORTSMOUTH, N.H. — State and federal scientists in New Hampshire and Maine are planning to release a dye into the Piscataqua River to help determine if the area is suitable for recreational shellfish harvesting.

Information from the dye-study that is to be held Tuesday will be used by the New Hampshire Department of Environmental Services, the Maine Department of Marine Resources and other organizations to determine whether areas of the Lower Piscataqua River are safe for shellfish harvesting and commercial shellfish operations.

The dye will be released early Tuesday from the Portsmouth wastewater treatment facility on Peirce Island for about 12 hours. Portions of the river may turn reddish in Portsmouth, New Castle, Rye, and Kittery, Maine.

The dye is not harmful to humans or the environment.