During
the 18th and 19th centuries dolphins were hunted commercially,
especially for the small quantity of valuable oil in
parts of the head. This oil was used to lubricate delicate
watch mechanisms;  cheaper
oils have now been found from other sources. Today dolphins
are less often hunted, although some cultures continue
to take dolphins for food.
In the second half of the 20th century, new tuna-fishing
techniques threatened many populations of dolphins.
Some dolphin species, including spinner, spotted, and
common dolphins, commonly swim with schools of tuna.
Tuna boats follow these dolphins, hoping the dolphins
will lead them to the tuna. In the 1960s tuna fleets
began to use purse seine nets, large nets that encircle
tuna and any nearby dolphins, trapping them when the
nets are pulled shut at one end. When the purse seine
net is pulled aboard the tuna boat, the dolphins often
die before they can be released from the net. From 1959
to 1972 an estimated 4.8 million dolphins died in this
way.
Conservationists fought to reduce dolphin mortality
in the tuna-fishing industry. As a result of their efforts,
in 1990 the United States Congress passed the Dolphin
Protection Consumer Information Act (DPCIA). The DPCIA
requires that tuna canners can only label their products
as "dolphin-safe" if the tuna was harvested
using certain strict criteria. For instance, if there
is even one instance in which a tuna-fishing boat circles
dolphins with a purse seine net, the entire load of
tuna captured by the boat cannot be called dolphin-safe.
In recent years a number of tourist programs around
the world have developed in which humans are encouraged
to swim and interact with bottlenose dolphins at sea.
Scientists are concerned that such human interactions
can interrupt dolphin social activities or force them
to leave preferred habitats. In the United States, the
Marine Mammal Protection Act of 1972, amended in 1988
and 1992, prohibits feeding or harassing dolphins and
all marine mammals in U.S. waters.
 Scientific
classification: Dolphins belong to the suborder Odontoceti
(toothed whales) of the order Cetacea. The common bottlenose
dolphin is classified as Tursiops truncatus and the
Indo-Pacific bottlenose dolphin is classified as Tursiops
aduncus. The three species of common dolphin are classified
in the genus Delphinus. The five species of spotted
dolphins belong to the Stenella genus. The six species
collectively referred to as lags belong to the genus
Lagenorhynchus. The Irrawaddy river dolphin is classified
as Orcaella brevirostris. The Amazon river dolphin is
classified as Inia geoffrensis, the Indian river dolphin
as Platanista gangetica, the Chinese river dolphin as
Lipotes vexillifer, and the Franciscana as Pontoporia
blainvillei. |
