Stenella coeruleoalba

 Stenella coeruleoalba is a toothed whale and can be recognised as such by the single blowhole and the presence of teeth (rather than baleen). It is a member of the dolphin family with a characteristic prominent median notch in the flukes, a smooth crease-less throat and sharply pointed teeth. The striped dolphin reaches up to 2.6 m in length. It has long and slender flippers and small tail flukes. The dorsal fin is tall and narrow-based and located on the middle of the back. The head is smoothly sloping with a distinct snout. It has a complex colour pattern, with shades of black to dark grey on the back changing sharply to light grey on the sides and white underneath. It has a prominent black stripe that runs from the eye to the anus, and usually other shorter black stripes originating at the eye.Striped dolphins are usually found in large pods of up to 500 individuals. Mixed schools with other species have been recorded. Their surface behaviour is typical of dolphins with leaps and bow-riding a common sight. Dives may last up to 20 minutes long (Kinze, 2002).

A highly gregarious animal, the striped dolphin may associate in schools of over 1000, but is more usually seen in same-age groups of 100 to 500 individuals (6). It is a very active swimmer, performing leaps and breaching frequently. Communication between striped dolphins is by clicks and whistles (7). The striped dolphin feeds opportunistically, but the diet is mainly composed of cephalopods, crustaceans and fish, particularly lantern fish. The diet varies with geographical location (8). The mating season also varies with region. Males reach sexual maturity between 7 and 15 years and females between 5 and 13 years. The gestation period lasts 12 to 13 months and results in a single calf measuring less than a metre and weighing just 11 kilograms. The calf will stay with the female in a 'mothers-and-calves' school until it is weaned at 16 months. Females typically give birth every four years (6) (9).

With the classic dolphin shape, the striped dolphin's most remarkable feature is the distinctive pattern of blue and white stripes along the body. It is mainly blue with a white to light grey stripe following the spine. The sides are darker than the belly (4). The beak is fairly long and prominent, the dorsal fin is tall, and the flippers are long and narrow with black stripes (6)

Stenella coeruleoalba is found in warm-temperate and tropical seas throughout the world. S. coeruleoalba has been observed in the Mediterranean Sea, eastern and western Pacific Ocean, Atlantic Ocean, Indian Ocean, Caribbean Sea, and in the northern Gulf of Mexico (Baird et. al., 1993; Archer and Perrin, 1999).

Biogeographic Regions: indian ocean (Native ); atlantic ocean (Native ); pacific ocean (Native )

circum-global between 50°N and 40°S

Nova Scotia south to at least Jamaica and in the Gulf of Mexico

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Transient

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: Tropical, subtropical, and warm temperate oceans. Reportedly the most common cetacean in Mediterranean Sea. Proposed discrete stocks: one off South Africa, one or two in the eastern tropical Pacific, and another in the western North Pacific (see IUCN 1991). Widely distributed and relatively common.

The striped dolphin is found in all temperate and tropical waters, throughout the Atlantic Ocean, Pacific Ocean, Indian Ocean, Mediterranean Sea and Black Sea (1).

Stenella coeruleoalba, otherwise known as striped dolphins, are a fascinating member of the family Delphinidae. S. coeruleoalba ranges in body length from 220cm to 236cm. Like many other delphinids, striped dolphins have a fusiform body, tall dorsal fins, long, narrow flippers, and a prominent beak (Archer and Perrin, 1999). S. coeruleoalba can be identified from other delphinids by their distinctive color and stripe patterns. Striped dolphins are typically bluish-gray in color with a dark dorsal cape and light (usually white) ventral coloration. They are called 'striped' dolphins because of the dark bluish-black stripe running across the entire length of the body, from the eye to the anus, and because they possess black flipper stripes (Archer and Perrin, 1999).

Range mass: 135.9.5 to 0.16 kg.

Average mass: 0.15 kg.

Length: 270 cm

Striped dolphins occupy both offshore and inshore warm-temperate and tropical waters. S. coeruleoalba appears to avoid sea surface temperatures of less than 20 degrees C (Van Waerebeek et. al., 1998).

Aquatic Biomes: benthic ; reef ; coastal

oceanic

Depth range based on 2957 specimens in 1 taxon.
Water temperature and chemistry ranges based on 1770 samples.

Environmental ranges
  Depth range (m): 0 - 0
  Temperature range (°C): 6.894 - 29.365
  Nitrate (umol/L): 0.035 - 10.235
  Salinity (PPS): 31.551 - 39.131
  Oxygen (ml/l): 4.396 - 7.195
  Phosphate (umol/l): 0.041 - 0.897
  Silicate (umol/l): 0.818 - 6.989

Graphical representation

Temperature range (°C): 6.894 - 29.365

Nitrate (umol/L): 0.035 - 10.235

Salinity (PPS): 31.551 - 39.131

Oxygen (ml/l): 4.396 - 7.195

Phosphate (umol/l): 0.041 - 0.897

Silicate (umol/l): 0.818 - 6.989
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

Habitat Type: Marine

Comments: Warm temperate and tropical seas; inhabits offshore and coastal waters; usually offshore in most areas. Young are born in the water.

 The striped dolphin is an oceanic species, found down to several hundred metres, but may occasionally come close to shore in deeper areas.

The striped dolphin inhabits temperate and tropical pelagic waters (1).

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

In the western Pacific, makes seasonal migrations between pelagic and coastal areas; summers in pelagic waters, winters apparently in East China Sea (Leatherwood and Reeves 1983).

S. coeruleoalba seems to have an opportunistic feeding habit. Examining the stomach contents of many striped dolphins, researchers have found S. coeruleoalba to mainly feed on cephalopods, crustaceans, and bony fishes (Wuertz and Marrale, 1993). There is some variation in diet between ranges of S. coeruleoalba. Mediterranean striped dolphins seem to prey primarily on cephalopods (50-100% of stomach contents), while northeastern Atlantic striped dolphins most often prey on fish, frequently cod (Archer and Perrin, 1999). The ranges of observed prey indicate that striped dolphins primarily feed in pelagic or benthopelagic zones of the ocean, often along the continental slope (at the edge of the continental shelf where the ocean floor plunges steeply four to five kilometers) (Archer and Perrin, 1999).

Animal Foods: fish; mollusks; aquatic crustaceans

Primary Diet: carnivore (Piscivore , Molluscivore )

Comments: Diet mainly various mesopelagic fishes, as well as shrimp and squid (Leatherwood and Reeves 1983). Feeding depth may extend below 200 m (see IUCN 1991).

Gregarious; commonly in groups of a few hundred, sometimes in herds of several thousand; group size in the Atlantic apparently tends to be smaller than that in the Pacific (IUCN 1991); groups are segregated by age class (Leatherwood and Reeves 1983, IUCN 1991).

Comments: Active day/night.

Average lifespan
Status: wild: 50.0 years.

Maximum longevity: 57.5 years (wild) Observations: It has been estimated that these animals may live up to 57.5 years in the wild. One 48.5 year-old females has been found pregnant (Archer and Perrin 1999).

The age of sexual maturity is quite variable within sexes. Males reach sexual maturity between the ages of 7 and 15, and females become sexually mature between 5 and 13 years of age. The mating season of the striped dolphin is in the winter and early summer in the western north Pacific, while it occurs in the fall in the Mediterranean (Archer and Perrin, 1999). The gestation period of striped dolphins lasts 12-13 months. Females typically have a four year calving interval, having a resting period of approximately 2-6 months between lactation and the next mating (Calzada et al., 1996).

Breeding interval: Females typically have a four year calving interval

Breeding season: The mating season of the striped dolphin is in the winter and early summer in the western north Pacific, while it occurs in the fall in the Mediterranean

Average number of offspring: 1.

Range gestation period: 12 to 13 months.

Range weaning age: 16 (high) months.

Average weaning age: 16 months.

Range age at sexual or reproductive maturity (female): 5 to 13 years.

Range age at sexual or reproductive maturity (male): 7 to 15 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous

Average birth mass: 10000 g.

Average number of offspring: 1.5.

Fetuses grow at an approximate rate of 0.29cm/day. At birth, striped dolphins are 90-100cm long (differing slightly between ranges) and weigh approximately 11.3kg (Calzada, Aguilar, Sorensen, and Lockyer, 1996). Young calves then nurse for almost 16 months. (Archer and Perrin, 1999; Calzada et. al., 1996).

Parental Investment: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female)

In the western Pacific, mating peaks in winter, spring, and possibly late summer; gestation lasts about 1 year; adult females produce single calf every 3 years; weaning completed at about 1.5 years; sexual maturity in 5-9 years, though newly mature males may not mate.

S. coeruleoalba is currently listed at Lower Risk in the IUCN - Red List. It is further categorized as being "Conservation Dependent," meaning that the species is in a taxa that is the focus of a conservation program. Without a conservation program, the striped dolphin will qualify for a threatened/endangered status within five years.

Habitat degradation, commercial fisheries, and killing dolphins for their meat all contribute to striped dolphin population declines.

US Federal List: no special status

CITES: appendix ii

IUCN Red List of Threatened Species: least concern

Accidental?

Canada

Rounded National Status Rank: NNA - Not Applicable

United States

Rounded National Status Rank: NU - Unrankable

Rounded Global Status Rank: G5 - Secure

Classified as Least Concern (LC) on the IUCN Red List (1), and listed on Appendix II of CITES (3). It is also listed on Appendix II of the Convention on Migratory Species (4). All cetaceans (whales and dolphins) are listed on Annex A of EU Council Regulation 338/97; they are therefore treated by the EU as if they are included in CITES Appendix I, so that commercial trade is prohibited. In the UK all cetaceans are fully protected under the Wildlife and Countryside Act, 1981 and the Wildlife (Northern Ireland) Order, 1985 (5).

Comments: Comprises a minor component of dolphins killed by purse-seine tuna fishery in eastern tropical Pacific. There is some concern about the levels of direct and indirect catching in various parts of the range (IUCN 1991). Population off Japan declined from the mid-1940s through at least the early 1980s, due to overexploitation (see Baird et al. 1993).

Once a substantial threat, by-catch has been reduced from 14,000 striped dolphins a year between 1950 and 1969 in the western Pacific, to a current incidental catch of 2,000 to 4,000 individuals. Fishermen kill dolphins caught in their nets as they present competition for fish (7). Hunting has also been known to take place, particularly in Japan, but is not considered a major threat, and Japan has voluntarily reduced its catch. Water pollution as a result of the release of heavy metals causes lung disease, and the over-fishing of anchovies has harmed populations in some areas (4). In the Mediterranean Sea, a morbillivirus caused the death of more than 1,000 animals between 1990 and 1992. The epidemic was possibly caused by poor environmental conditions (1).

A UK Biodiversity Action Plan priority species, the striped dolphin is protected in UK waters by the Wildlife and Countryside Act 1981 and the Wildlife (Northern Ireland) Orders, 1985; it is illegal to intentionally kill, injure, or harass any cetacean (whale or dolphin) species in UK waters (5). The Agreement on the Conservation of Small Cetaceans in the Baltic and North Seas (ASCOBANS) has been signed by 7 European Countries, this includes the UK. Provision is made under this agreement to set up protected areas, promote research and monitoring, pollution control and increase public awareness (5).

Striped dolphins are in constant competition with humans over prey. The dolphins and fisheries compete over anchovies, tuna, and cod. Fisherman often kill striped dolphins that are caught in their fishing nets. The number of striped dolphins killed in the western Pacific was estimated at 14,000 each year between 1950-1969, but more recently has decreased to between 2,000 and 4,000 per year (  http://www.cetacea.org/striped.htm, 1998).

Striped dolphins provide much entertainment to sailors and travelers, as they flip, twist, and breach alongside the waves created by ships and boats. In addition, they are sometimes hunted for meat.

Comments: Hunted by fishermen (harpooning, herding) in Japan for many centuries (annual catch in 1960s and 1970s was 10,000-20,000; 16,000 in 1980; 2918 in 1986). Included in native catch of small cetaceans around southwest Pacific islands (Leatherwood and Reeves 1983).

Least Concern (LC)