SCIENTIFIC NAME: Stenella attenuata

COMMON NAME: Pantropical Spotted Dolphin

GEOGRAPHICAL DISTRIBUTION:

Distribution not continuous within the range, though it appears to be abundant in many areas
Well-studied in the eastern tropical Pacific but poorly known elsewhere
Overlaps with the Atlantic Spotted Dolphin, mainly in the western North Atlantic, where it occurs offshore
No known migrations, though offshore form may make seasonal movements, usually summering inshore and wintering offshore

DESCRIPTION:

Dark gray cape
Dark line from flipper to beak
Tall, falcate fin
Slender, elongated body
Long narrow beak
White-tipped beak and "lips"
Most adults heavily spotted
Appearance varies within school
Spotting varies with age and location
Spots increase in size and number with age

NATURAL HISTORY:

HABITAT:

Widely distributed, mainly in the tropical, subtropical, and temperate waters of the Atlantic, Pacific, and Indian Oceans
Found mainly where surface water temperature higher than 77 degrees (25 degrees C)
Commonly occurs around island

FOOD & FEEDING:

Stomach contents of recorded dolphins include a large number of small epipelagic and mesopelagic fish and cephalopod species, nemerten worms and crab larvae
Lactating females may feed more heavily on epipelagic fish than do pregnant females

LIFE CYCLE:

Average age at sexual maturity in males is 14.7 years and females mature on the average at 10-12 years, with a range of 10 to 17 years
Maximum longevity in both sexes may exceed 45 years
Length at birth= 0.85m in the offshore eastern tropical Pacific
Breeding is diffusely seasonal- two to three calving seasons in the spring, autumn, and summer
Average calving interval in the eastern Pacific= 2-3 years in the western Pacific 4-6 years

BEHAVIOR:

Very active at surface
Fast, energetic swimmer, using long, shallow leaps
Frequently breaches
Lobtailing and bow-riding common
In tuna fishing areas some individuals flee from boats

WORLD POPULATION:

Studies have been made of the eastern tropical Pacific populations involved in the tuna purse seine fishery
No other studies done
Average of 2.5 million in 1981-86

HUMAN INFLUENCES:

Major by-catching problems in the eastern tropical Pacific due to the habit of schooling with tuna
Estimated that about 70,000 offshore pantropical spotted dolphins were killed during tuna purse seining in 1986 (Costa Rica, Ecuador, El Salvador, Mexico, Panama, Spain, USA, Vanuatu and Venezuela), 693 by direct catches in Japanese waters and that some were taken incidently in Australian waters- some also taken in at least the Caribbean, Sri Lanka and the Solomon Islands
Several dolphins also killed in efforts to reduce the interference in a hook-and-line fishery for yellowtail tuna off Iki Island in Japan