The warm, tropical waters surrounding the Hawaiian Islands are home to resident populations of dolphins. Hawaii hosts several distinct species, with some preferring deep ocean trenches and others consistently frequenting calm, nearshore bays. Because these intelligent marine mammals are protected under federal law, specific regulations govern all human interactions with them.
The Common Dolphin Species of Hawaii
The most frequently encountered dolphin in the nearshore waters of Hawaii is the Hawaiian Spinner Dolphin (Stenella longirostris), named for its distinctive aerial acrobatics. These relatively small dolphins typically measure between 4.6 and 6.8 feet and weigh around 170 to 181 pounds. They exhibit a tripartite color pattern: a dark gray back, a light gray side, and a white belly, which aids in camouflage.
The second most common resident is the Bottlenose Dolphin (Tursiops truncatus), which is noticeably larger than the spinner dolphin. They have uniform gray coloration and a thicker, blunter rostrum (snout) compared to the spinner’s slender beak. Bottlenose dolphins are highly social and often travel in smaller pods, sometimes playing in boat wakes.
A third species often seen near the islands is the Pantropical Spotted Dolphin (Stenella attenuata). While similar in size to the spinner dolphin, adults are easily distinguished by a unique pattern of spots covering their bodies and a white-tipped beak. Less common species, such as the Rough-toothed Dolphin (Steno bredanensis) and Risso’s Dolphin (Grampus griseus), are typically found further offshore in deeper, pelagic waters.
Hawaiian Dolphin Habitats and Behavior
Dolphin distribution in Hawaii is influenced by daily behavioral needs, distinguishing between nearshore and offshore habitats. Hawaiian spinner dolphins exhibit a daily fission-fusion cycle. They spend their nights in the deep ocean, often diving 650 to 1,000 feet to feed on the mesopelagic layer, consuming small fish, squid, and shrimp.
As the sun rises, spinner dolphins return to sheltered, shallow bays and coves. These nearshore areas, typically less than 50 meters deep, serve as daytime resting grounds where the dolphins recover from nocturnal foraging. During this period, they move slowly in tight formations, resting, socializing, and nursing their young, relying on the calm water to avoid predators.
Bottlenose and spotted dolphins are also found near the islands but do not rely on shallow bays for daily rest like the spinners. Spotted dolphins are more often sighted traveling through the deeper channels between the islands. The predictable use of accessible bays by spinner dolphins made them vulnerable to human disturbance, leading to specific protective regulations.
Responsible Viewing and Legal Protections
All marine mammals in the United States, including Hawaiian dolphins, are protected under the Marine Mammal Protection Act (MMPA). The MMPA prohibits “take,” defined as harassment or disturbance. To address the chronic disturbance of resting spinner dolphins, NOAA Fisheries implemented a final rule in 2021. This regulation strictly prohibits swimming with, approaching, or remaining within 50 yards (45.7 meters) of a Hawaiian spinner dolphin.
This required distance applies to all persons, vessels, and objects, including kayaks, paddleboards, and drones. The rule is enforced in all waters within two nautical miles of the main Hawaiian Islands and within the designated waters bounded by Lānaʻi, Maui, and Kahoʻolawe. The regulation also bans “approach by interception,” meaning placing a vessel or person in the dolphin’s path intending to breach the 50-yard buffer.
The rule’s intent is to minimize the disruption of the dolphins’ daytime resting behavior, which is necessary for their health and survival. Violations of the federal law can result in significant civil penalties. Responsible viewing involves remaining stationary outside the 50-yard perimeter and allowing the dolphins to approach or depart freely.