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Scientific name: Stenella longirostris longirostris
Pacific Island names: nai'a (Hawaiian), mumua (Samoan)
Current Management Issues
On August 23, 2016, NOAA Fisheries published a proposed rule to enhance protections for Hawaiian spinner dolphins to prevent disturbance and harassment from dolphin-directed human activities. The proposed rule would prohibit swimming with and approaching a Hawaiian spinner dolphin within 50 yards by any means (vessel, person, or other object) and would be implemented within two nautical miles from shore of the Main Hawaiian Islands and in designated waters between Maui, Lanai, and Kahoolawe where spinner dolphins are found throughout the day.
Resident populations of Hawaiian spinner dolphins feed offshore throughout the night and return to Hawaii's coasts to rest during the day. Because Hawaiian spinner dolphins rest in Hawaii's sheltered bays and along its coastlines and are one of the most easily encountered cetaceans in the waters of the Main Hawaiian Islands, they are vulnerable to disturbance and harassment. 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. Chronic disturbance to resting activities can negatively affect the health and fitness of dolphins.
The proposed rule is based on the preferred alternative (Alternative 3A) in the Draft Environmental Impact Statement. Other alternatives considered include the following:
- Alternative 1 — No Action
- Alternative 2 — Swim-With Regulation
- Alternative 3 — Swim-With and Approach Regulations
- 3(A) — Swim-With and 50-Yard Approach Regulations (Preferred Alternative)
- 3(B) — Swim-With and 100-Yard Approach Regulations
- Alternative 4 — Voluntary Time-Area Closures in 5 Selected Essential Daytime Habitats and Swim-With and Approach Regulations
- Alternative 5 — Mandatory Time-Area Closures in 5 Selected Essential Daytime Habitats and Swim-With and Approach Regulations
- For the Proposed Rule for Spinner dolphins, please see here.
- For the Proposed Rule references, please see here.
- For the Draft Environmental Impact Statement and Regulatory Impact Review, please see here.
- For Frequently Asked Questions (FAQ): Spinner dolphins, please see here. (August 2016)
- For the Press Release, please see here. (August 23, 2016)
Can I Still Submit Comments?
The public comment period is closed.
- View comments: Go to https://www.federalregister.gov/d/2016-27399 via the Federal eRulemaking Portal.
- Public Meetings: NOAA Fisheries invited the public to learn more about the proposed rule and to provide comments in person at six public hearings. The dates, times, and locations for the hearings that were held are listed below.
- September 7, 2016, 5:30-9:30 p.m.
Konawaena High School Cafeteria, 81-1043 Konawaena School Rd., Kealakekua, Hawaii 96750
- September 8, 2016, 5:30-9:30 p.m.
Kealakehe High School Cafeteria, 74-5000 Puohulihuli St., Kailua-Kona, HI 96740
- September 21, 2016, 5:30-9:00 p.m.
Kauai High School Cafeteria, 3577 Lala Rd., Lihue, HI 96766
- September 22, 2016, 5:30-9:00 p.m.
Hawaiian Islands Humpback Whale National Marine Sanctuary Visitor Center, 726 S. Kihei Rd., Kihei, HI 96753
- September 27, 2016, 5:30-9:30 p.m.
Roosevelt High School Cafeteria, 1120 Nehoa Street, Honolulu, HI 96822
- September 28, 2016, 5:30-9:30 p.m.
Waianae High School Cafeteria, 85-251 Farrington Hwy
- September 7, 2016, 5:30-9:30 p.m.
For more information about Spinner dolphins and the proposed rule, please visit:
Spinner Dolphin - Human Interaction EIS and Rule-making page.
Stock Assessment / Estimated Breeding Population
Hawaii has 5 distinct island-associated stocks of Hawaiian spinner dolphins. The stocks are as follows: 1) Midway/Kure, 2) Pearl and Hermes Reef, 3) Kauai and Niihau, 4) Oahu/4-islands (including Maui, Lanai, Molokai, Kahoolawe), and 5) Hawaii Island. These stocks live in coastal waters ranging to 10 nautical miles from the shore of their resident islands. All other spinner dolphins found outside of 10 nautical miles and within the U.S. Exclusive Economic Zone (including those at French Frigate Shoals) are part of the Pelagic stock. These stocks are reproductively isolated populations, meaning that there is little to no breeding occurring between stocks (Andrews, 2009).
A robust estimate for population size is only available for the Hawaii Island stock, which is estimated to be around 600 animals. The Kauai/Niihau stock is estimated to be around 500 animals and Oahu/4-Islands stock is estimated to be around 300 animals; however, both of these estimates lack data from the stocks' full range. Information is insufficient to provide estimates for the other three stocks.
For species-specific stock assessment information, please see here.
All marine mammals are protected from "take" under the MMPA. The MMPA defines take to mean "to harass, capture, or kill" any marine mammal or attempt to do so. Harassment is further defined by the MMPA as any act of pursuit, torment, or annoyance that has the potential to do the following:
- Level A harassment - injure a marine mammal or marine mammal stock in the wild; or
- Level B harassment - disturb a marine mammal or marine stock in the wild by causing disruption of behavioral patterns, including but not limited to migration, breathing, nursing, breeding, feeding, or sheltering.
When viewing spinner dolphins in the wild, people must ensure their activities will not result in "take." For responsible viewing guidelines provided by NOAA Fisheries, please see here.
Spinner dolphins are probably the most frequently encountered cetacean in waters of the Pacific Islands Region. They get their common name from the impressive spins they perform during social encounters. Spinners spend their daylight hours in coastal waters, generally in calm bays. They use these areas to rest, care for their young and to avoid predators, before traveling to deeper water at night to hunt for food. Spinner dolphins have what is called a "fission fusion social pattern." They "fuse" to form large schools of hundreds of animals when feeding at night and split off into much smaller groups, sometimes of only a dozen individuals, when socializing and resting during the day.
- Individual dolphins will generally grow from 4 to 7 feet in length and weigh between 100 and 165 pounds.
- Each has a long narrow beak, dark grey dorsal cape, medium grey flanks and a light grey/whitish belly.
- Individual dolphins are identified by their unique dorsal fins. Researchers take photographs of the animals' dorsal fin, and the shape, nicks, and notches in each fin can then be matched to a catalog of known individuals to obtain life history information for each animal.
- Spinner dolphins feed at night on species from the mesopelagic community, including shrimp and squid that are found about 650-1,000 feet below the surface of the water. Spinner dolphin prey species follow a vertical and horizontal migration pattern throughout the day, staying in deep waters in the ocean during the day, and then moving up in the water column (vertical migration) and inshore (horizontal migration) at night. Spinner dolphins take advantage of the nightly migration that brings their prey species to shallower depths closer to shore by feeding throughout the night.
- A spinner dolphin's lifespan is estimated to be about 20 years.
- Spinner dolphins do not have a mating or birthing season. They mate, give birth, and care for their young year round.
- Potential threats include entanglement in marine debris, anthropogenic (human made) noise, pressure from human viewing and interaction activities, disease, and fisheries interactions.
- Remain at least 50 yards from spinner dolphins
- Limit your time observing to 1/2 hour.
- Spinner dolphins should not be encircled or trapped between boats or shore.
- If approached by a spinner dolphin while on a boat, put the engine in neutral and allow the animal to pass. Boat movement should be from the rear of the animal.
Important Phone Numbers
Marine Mammal Stranding/Entanglement Hotline: 1-888-256-9840
- Federal Register Notice of Intent (Oct 2006, pdf 67kB)