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spots; posterior to
the dorsal fin the blackish upperparts and the flippers often covered with
grayish white dots. Teeth small (diameter at alveolus 2.5-3.0 mm) and
38-42 in each toothrow. Total length, 1.5-2.0 m. Similar to
S.
frontalis but upperparts blackish, general
size smaller, beak narrower, and the teeth smaller and more numerous.
Distribution in Texas
Occurs in the tropical and subtropical oceans of the world. Known in Texas
from three individuals that were beached near Yarborough Pass on Padre
Island during Hurricane Fern in September, 1971, and two separate
individual strandings near Port Aransas in 1989 and 1990.
Habits
These dolphins are usually seen in groups of five to 30, although large
herds of 1,000 or more are occasionally observed. Unlike many other
dolphins, groups of pantropical spotted dolphins do not appear to be
segregated by sex and age. These dolphins feed at or near the surface on
fish, including mackerel and flying fish, squid, and shrimp.
In the eastern tropical
Pacific, the following reproductive data are known. The gestation period
lasts 11.5 months and lactation lasts about 11 months. At birth the calves
average 80 cm in length and at 1 year are 1.4 m long. Males attain sexual
maturity at about 6 years of age while females reach maturity at 5 years.
The calving interval is 26 months. No data on reproductive habits are
available for the Gulf of Mexico.
In the Pacific, these
dolphins are killed incidentally in the course of seining for tuna. In
1970, about 400,000 were killed by U.S. vessels alone but that figure was
reduced to 15,000-20,000 by 1978. Currently, incidental catch is limited
by U.S. law to 20,500 per year but is usually lower than that due to
declining tuna seining efforts and the recent adoption of a porpoise
mortality reduction program; this international agreement by all major
tuna seining countries has a goal of reducing total incidental catch to
less than 5,000 dolphins per year by 1999. In the Atlantic and Gulf of
Mexico, the problem of incidental catch is limited and was never as great
as in the Pacific.
Remarks
This dolphin was previously known as Stenella frontalis (Cuvier). |
