The National Marine Fisheries Service (NMFS) has proposed a ban on human contact with Hawaiian spinner dolphins, potentially cutting the revenue stream for a popular tourist activity.

The proposal, which would prohibit people swimming within 50 yards (150ft) of the animals, would be implemented to address disturbance of the dolphin’s sleeping patterns.

Hawaii’s spinner dolphins feed offshore at night, returning to shallower waters during the day to rest, which is a problem because that’s when tourist dolphin tours operate.

“Dolphin-directed activities have grown dramatically in recent years, and the easily accessible Hawaiian spinner dolphins face heavy and increasing pressures from people seeking a dolphin experience,” the agency said. “Chronic disturbance to resting activities can negatively affect the health and fitness of dolphins.”

The government previously passed similar regulations preventing people from getting within 100 yards (300ft) of humpback whales in Hawaii and Alaska and orcas in the Puget Sound. This would be the first US legislation to cover dolphins. NMFS is planning public meetings on the plan, with a final decision to be made in 2017.