A cadre of recreational ocean users and water-sport business owners demonstrated Saturday afternoon in opposition to a proposed expansion of the scope and jurisdiction of the Hawaiian Islands Humpback Whale National Marine Sanctuary.

Bearing signs that read “No Fishing?” and “Say No to NOAA” — a reference to the National Oceanic and Atmospheric Administration, which proposed the plan — protesters lined Kalanianaole Highway fronting Maunalua Bay in Hawaii Kai.

Introduced in March, the NOAA proposal called for increasing the size of the sanctuary by 17 percent and expanding its focus to the protection of all marine species within its boundaries, essentially transitioning the sanctuary from one that serves a single species to one charged with protecting whole ecosystems.

Demonstrators expressed concern that the plan and its associated regulations would unduly restrict recreational ocean use and negatively affect businesses that operate in coastal areas.

Frazer McGilvray, executive director of Malama Maunalua, a nonprofit group dedicated to restoring and protecting Maunalua Bay, defended the proposal.

“The decline of Maunalua Bay is serious — the worst in the state,” McGilvray said in a statement released Saturday afternoon. “NOAA’s proposal represents an opportunity to protect and restore the bay, ensuring this beloved ecosystem survives for the enjoyment of our children and their children.”

McGilvray emphasized that proposed changes to existing regulations would not impact normal ocean activity.

“Recreational use of Maunalua Bay is not in danger,” McGilvray said. “This includes fishing, anchoring, scattering of ashes and other current uses. I enjoy the Bay as much as my neighbors and would not support taking anything away from our quality of life on this side.”

The sanctuary was founded in 1992 and remains the only U.S. sanctuary dedicated to a single species.

Under the plan, Special Sanctuary Management areas would be established at Maunalua Bay, Penguin Bank off western Molokai, and waters of Maui County, with restrictions against taking and possessing marine species, altering submerged lands, setting off explosives and introducing nonnative species.

A series of informational meetings was presented around the state in April and May.

Public comments on the draft management plan, proposed regulations and draft environmental impact statement are being accepted through Friday. For more information, visit 808ne.ws/1QwA7o8.