Spinner dolphin
Spinner dolphin ( Stenella longirostris )
The East Pacific dolphin ( Stenella longirostris ) is a species of spotted dolphins (Stenella ). He is also known as the spinner dolphin known ( from English to spin ), because of this species perform jumps, in which they rotate as a drill quickly to their own body axis.
Features
The body length of the spinner dolphin varies but is usually in the range from 1.20 to 2.30 meters with a weight between 20 and 80 kg. Characteristic of all is a triangular, hardly crescent-shaped dorsal fin and a long, narrow snout. The East Pacific dolphin is dark gray on the upper side and lower side creamy white. On the base of the tail, the back and the throat is dark patches can stand out. The muzzle is pulled conspicuously long and has a dark tip. There are several sub- types, which may differ from each other in their coloring and shape.
In the Atlantic, there is a likelihood of confusion with the Clymene dolphin, which behaves similarly.
Behavior
As social animals include East Pacific dolphins in groups of a few to several thousand animals together. They are very playful and acrobatic and known to "ride " the bow waves of boats. The reason for their characteristic rotation is unknown, with single copies have watched performs up to 14 of these " spinnings " in a row.
Dissemination
East Pacific dolphins are indeed in the eastern Pacific, about off Hawaii and Mexico, the frequently encountered, however, widespread in tropical seas worldwide. They prefer deep sea areas of the high seas.
Taxonomy
The East Pacific dolphin was described by John Edward Gray in 1828 for the first time and got the name " longirostris " due to the long snout. Today, this type of four subspecies are distinguished:
- S. L. orientalis as eastern subspecies in the eastern tropical Pacific.
- S. l centro americana in the area of Central America, Costa Rica, also in the eastern Pacific.
- S. L. longirostris than nominate also known as Gray's Spinner Dolphin in the central Pacific, especially to Hawaii.
- S. l roseiventris, the smallest form, was first discovered in the Gulf of Thailand.
In addition to these forms, there is a great variability, with some color variations are typical for individual regions and populations.
Threat
The East Pacific dolphin currently is not considered threatened. The living in the tropical eastern Pacific populations are often associated with yellowfin tuna fish. A biological phenomenon that occurs only in this marine region. Because a dolphin school is easy to observe from boats or helicopters, the dolphin school was encircled with a purse seine, which was then drawn from the bottom in the tuna fishery. In this way, more than 7 million dolphins came between the late 50s and the 90s of the 20th century as bycatch to death.
The stocks in the eastern tropical Pacific have not yet recovered from this, one assumes that about half of the total population disappeared there. The total population is about 900,000.