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Spinner Dolphin (Stenella longirostris)

Status | Species Description | Habitat | Distribution | Population Trends | Threats | Conservation Efforts | Regulatory Overview | Taxonomy | Key Documents | More Info

Status

MMPA Depleted - Eastern stock (Stenella longirostris orientalis) in the Eastern Tropical Pacific Ocean
CITES Appendix II - throughout its range

Species Description

Weight:
approximately 130 to 170 lbs (59-77kg)
Length:
6 to 7 feet (2m)
Appearance:
They have long, slender snouts or beaks. There is a great deal of color variation depending on the region
Lifespan:
20 years
Diet:
mid-water fishes and deep-water squid
Behavior:
Spinner dolphins feed primarily at night while resting for most of the daylight hours, Spinner dolphins are best known for their above-water displays of leaping and spinning several times, with up to 14 leaps in a row

Subspecies of the spinner dolphin include:

Like other dolphins of the genus Stenella, spinner dolphins are relatively small, reaching lengths of 6 to 7 feet (2 m) and weighing approximately 130 to 170 pounds (59-77 kg) at adulthood. They have long, slender snouts or beaks. There is a great deal of color variation depending on the region.

Spinner dolphins are best known for their above-water displays of leaping and spinning several times on their body axis. Leaps can often be done in a series with as many as 14 leaps in a row. Spinner dolphins are sometimes found in associations with bottlenose dolphins or humpback whales in Hawaii, which may benefit one or both species.

Mating and calving occurs year-round, with gestation similar to that of most dolphins, around eleven months. Multiple males may mate with one female in short, consecutive intervals. Lactation often takes place for two years, but can also last for only one year. Calving intervals average three years. Maturity occurs at around 7 years of age and maximum longevity is 20 years.

Spinner dolphins often occur in groups of several hundred to several thousand animals. They are considered quite gregarious, often schooling in large groups and with other dolphin species, such as spotted dolphins.

Spinner dolphins feed primarily at night on mid-water fishes and deep-water squid, while resting for most of the daylight hours.

The MMPA "depleted" eastern spinner dolphin (Stenella longirostris orientalis) is one of four named subspecies in the Pacific Ocean.

Habitat

In most places, spinner dolphins are found in the deep ocean where they likely track prey. The Hawaii population has a more coastal distribution. There, the animals rest in bays and protected areas during the day and then fuse into larger groups to feed in deeper water on fish and squid at night.

Distribution

The species can be found in all tropical and subtropical oceans. The eastern subspecies is found in the eastern tropical Pacific Ocean (ETP), often in groups of several hundred to several thousand animals.

Population Trends

The most recent stock assessment reports with population estimates are available on our website.

Threats

Due to the as yet unexplained association between large yellowfin tuna and some dolphin stocks in the ETP, the presence of the eastern stock of spinner dolphins has been used by the tuna purse-seine fishery to find tuna. Dolphins can become trapped in the nets and drown. Stress from becoming encircled in purse seines has also been documented as a very serious threat to dolphins. Currently, fishing methods for tuna imported into the U.S. under the Dolphin-Safe program do not allow fishing practices, such as setting on dolphins.

Interactions with tourists are a growing threat to the Hawaiian stock; because the species is active at night, daytime interactions with tourists inhibit necessary rest and sleep time.

Conservation Efforts

Spinner dolphins are classified as Lower Risk - Conservation Dependent on the IUCN Redlist This link is an external site.. The International Dolphin Conservation Program Act (IDCPA) [pdf] directed NMFS to determine if the chase and encirclement of dolphins in the purse seine fishery targeting tuna in the ETP is having a significant adverse impact on depleted dolphin stocks. As part of this determination, Congress specified that population surveys be undertaken in 1998, 1999, and 2000 to generate new estimates of dolphin abundance under the IDCPA.

Two programs run by NMFS' Southwest Fisheries Science Center aim to conserve spinner dolphins:

NMFS developed a viewing guide [pdf] for responsibly viewing spinner dolphins in Hawaii to protect them from excessive disturbance when they rest and socialize. The  recognizes responsible tour operators in Hawaii that follow viewing guidelines which prevent disturbance of spinner dolphins as they rest during the day.

Regulatory Overview

In 1993, the Eastern spinner dolphin (Stenella longirostris orientalis) stock was designated depleted.

NOAA Fisheries announced a proposed rule under the Marine Mammal Protection Act to enhance protections for spinner dolphins in the Main Hawaiian Islands to prevent disturbance. Find information on the proposed rule and how to provide comments here. public comment period has been reopened, provide comments through December 1, 2016.

Taxonomy

Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Cetacea
Family: Delphinidae
Genus: Stenella
Species: longirostris

Key Documents

(All documents are in PDF format.)
Title Federal Register Date
Depleted Designation for Eastern Spinner Dolphins 50 CFR 216.15 08/26/1993
Stock Assessment Reports (Western North Atlantic, Hawaii, Northern Gulf of Mexico) n/a various

More Information

 

Updated: November 15, 2016