Marine Mammals - Dolphins And Porpoises

Dolphins and porpoises are toothed cetaceans. They are similar in shape; however, dolphins are generally larger than porpoises and prefer shallower, warmer waters. Dolphins tend to have long bottlenoses and cone-shaped teeth, as opposed to the flatter noses and teeth found in porpoises. Porpoises are members of the Phocoenidae family, which includes only six existing species. Dolphins are members of the Delphinidae family, a large family containing at least thirty known species. Most dolphin and porpoise populations around the world are hardy and not in danger of extinction. However, there are several species that are in trouble due to limited geographical distribution.

There are no U.S. species of dolphin or porpoises listed under the ESA. There are three foreign species listed as endangered as shown in Table 5.1: the Chinese River dolphin, the Indus River dolphin, and the cochito. The Chinese River and Indus River dolphins live in freshwater rivers in China and Pakistan, respectively. Their numbers are considered to be extremely small. In both cases extensive river damming, water drawdown due to human consumption, fishing, and pollution are blamed for the declines.

The cochito (or vaquita) is a kind of porpoise found only in the Gulf of California, a narrow body of water that separates the western Mexican mainland from the Baja California peninsula. This stretch of water is known in the United States as the Sea of Cortez and contains a great diversity of sea life. Cochitos are among the rarest of all marine mammals. According to the NMFS the cochito species has been nearly eliminated because so many of the animals have become entangled in fishing lines and drowned.

Protection of Prevalent Dolphins

Although they are not considered endangered or threatened, dolphins receive special consideration under U.S. law because of public concern about them. Dolphins are believed to be highly intelligent. They have a high encephalization quotient, perhaps the highest of any animal, besides humans. In addition, many people have been exposed to dolphins through marine entertainment parks, movies, television shows, and even personal encounters and sightings at tourist beaches. As a result, there is widespread public fondness for the animals.

Dolphins are protected by the Marine Mammal Protection Act and laws designed to limit their capture during tuna fishing. In 1990 large U.S. tuna canning companies announced they would no longer purchase tuna caught in a manner that endangered dolphins. The companies began labeling their products "Dolphin Safe" if their practices met specific standards established by the U.S. government. The International Dolphin Conservation Program Act, passed in 1992, reduced the number of legally permitted dolphin deaths. This act also made the United States a dolphin-safe zone in 1994, when it became illegal to sell, buy, or ship tuna products obtained using methods that kill dolphins.