SCIENTIFIC NAME: Steno bredanensis

DISCOVERED: Lesson, 1828

COMMON NAME: Rough-Toothed Dolphin, Slopehead

GEOGRAPHICAL DISTRIBUTION:

Distribution is poorly known
Widespread in warm waters around the world- where sea temperature is above 77 degrees F (25 degrees C)
Avoids cold surface waters and cold currents
Sightings around Hawaii and off the coast of Brazil
Permanent population in the Mediterranean

DESCRIPTION:

Tall, falcate fin
Conical head
Beak continuous with forehead
Dark, narrow cape- may have purplish hue
Pinkish white blotches
Long, narrow beak
White "lips"
White or pinkish white below
Body robust in front of dorsal fin
Long, narrow beak
Broad flukes
Keels below and above tail stock
Some animals may be highly scarred
Dark patch around large eyes

NATURAL HISTORY:

HABITAT:

Deep tropical, subtropical, and warm temperate waters around the world

FOOD & FEEDING:

Mainly pelagic- pelagic octopus, squid and the remains of several species of pelagic fish have been found in stomachs

LIFE CYCLE:

Longest mature male was 2.65m and the longest female was 2.55m
Average length of sexually mature animals in the western North Atlantic was 2.32 m for males and 2.31 m for females
Longest reported foetus was 0.87m
Average ages of sexually mature animals in the Western North Pacific was 14 years for males and 10 years for females
Maximum ages of 32 and 30 years

BEHAVIOR

Difficult to observe
May be submerged as long as 15 minutes
Fast swimmer- sometimes porpoising with low, arc-shaped leaps
Swims with dorsal fin and small part of back clearly visible
Sometimes bow-rides- especially in front of fast-moving vessels
May associate with Bottlenose Dolphins and pilot whales- less frequently with spinner dolphins and spotted dolphins- occasionally with shoals of yellowfish tuna
May be seen logging
10-20 (1-50) - sometimes in groups of several hundred

WORLD POPULATION

Not thought to be particularly numerous in any specific area- observations of herds of several hundred animals have been made
May sometimes be confused with bottlenose dolphins
Observers have not yet located areas of high relative abundance

HUMAN INFLUENCES

Direct general fishery for small cetaceans in the West Indies
Very small numbers involved in the West Indies
Also small direct fisheries in the Soloman Islands, Papua New Guinea and Japan
Meat is used for human consumption
Accidental captures and stranded specimens have also been used for human consumption in West Africa
Small numbers taken in the Pacific tuna fishery
Small gillnet fisheries in Sri Lanka and probably elsewhere in the Indian Ocean
Incidental take in pelagic driftnet fisheries within the range