Interdisciplinary Minor in Global Sustainability
Senior Seminar (Instructor: Peter A. Bowler)
University of California, Irvine, March 1998 

Why Kill Dolphins?

By Daniel G. Nunez

Dolphins make up the largest and most diverse family of cetaceans. The family contains 26 recognized species of which 13 tend to have long well defined beaks and streamlined robust bodies. Many vary in size, shape, colors, beaks and flippers, as humans have various characteristics.

One of the most common dolphins that are found in southern California is the bottlenose dolphin (Kelly). The bottlenose dolphin is mainly found in coastal waters between 45 degrees north and 45 degrees south, also in Northern Europe waters. It is believed that there are two types of bottlenose dolphin regional wise: oceanic form and coastal form. This species is studied the most by biologists (Jefferson). The coastal population lives in fairly open groups with twenty or less in a pod, some groups are found to contain more in open ocean. It is not uncommon for these species to interact and breed with other species, as would a human interact with other diverse humans. The dolphins feeding behavior is adapted to the availability of resources. They sometimes are known to work together to catch fish from large schools, they also trail behind large fishing boats to catch what falls behind (Leatherwood).

A large problem today is the incidental exploitation of the bottlenose dolphins in the Black sea. The dolphins suffer from entanglement in gillnets, shark nets, shrimp trawls, and purse seine nets in the eastern pacific tropical tuna fishery.

In the past twenty years a large amount of bottlenose dolphin have been killed due to the tuna fishery. In the Eastern Pacific swim large schools of tuna, these shoals tend to be under herds of dolphins, for some unexplained reason. Because of this, fishermen can easily find schools of tuna. The tuna are being caught under purse seine nets, which encircles the shoals of tuna and then is pulled back on board the fishing vessel, catching both tuna and dolphin. Initially the mortality rate was 500,000 each year for dolphins alone. Although some efforts are made to encourage the dolphins to leave the net by backing down part of the net, which allows the dolphins to escape, there are still a large number of mortalities (Bryant). On the other hand, in the last few years there has been dramatic progress in stopping the fishing industries from using purse sine nets. It has been found that dolphins are in immediate danger of extinction if these fishing techniques don’t stop. According to Bologa; "the dolphin population has declined to just one percent of the number recorded 46 years ago. In 1950, he said, one million dolphins belonging to these species lived in the Black Sea. However, their numbers started decreasing soon after. By 1970 there was a population of 70,000 dolphins, by 1995 the school had reduced to 10,000" (Bologa). If the present rate of destruction continues, dolphins will cease to exist in the Black Sea by the turn of the century.

In 1990, the U.S. government established regulations, so that tuna caught without killing dolphins can be labeled as "dolphin safe". In the U.S. there are three canneries that bought this label, which is 75% of the U.S. consumer’s products (Bryant). This is a great start to protect these mammals, but consider the industry as a whole; in essence the U.S. is a very small portion of the entire fishing industry. The United States took action by creating a boycott on all fishing countries that have a high mortality rate on dolphins. These countries have lost over $100 million in export revenues since 1991 (Bryant). In order for the U.S. to lift the embargo imposed in 1991 on tuna from several countries whose fishing led to massive dolphin slaughters on the Pacific coast, these countries would have to each limit the mortality rate to 5,000 per year. Countries who have had this boycott on their industry were Mexico, Venezuela, Columbia, Costa Rica, Ecuador, and Panama (Nunez). If they follow the guidelines, the "dolphin safe" label would be allowed for them to use. If this is considered to be "dolphin safe", can we imagine what the definition of "dolphin unsafe" would be.

Direct exploitation is doing its job in declining the dolphin population. In Bacold City, Philippines several dolphins are being found dead of bullet wounds. It is believed that these dolphins are traveling along with schools of tuna and fishermen on board big vessels shot them so they would not disturb their fish catch (Gomez). Also the illegal commerce of dolphin meat called "muchame" and "sea pig" is a delicacy in Peru. The method used in the killing of these mammals used to be by net, harpoon and/or beating. When brought alive to port, paper and plastic bags were forced in their blowholes to asphyxiate them, their throats were cut and they bled to death. Although the Peruvian government passed a law in 1990 that prohibits the extraction, process and commercialization of dolphins, the fishermen continued to kill them. Another example is the problem of captivity, when dolphins are kept in captivity for unnecessary reasons, such as luxury and commercialization. Reasons for avoiding captivity is that more than 50% of dolphins die in the first 24 months of captivity due to the fact that their life span and quality of life diminishes, and it’s nearly impossible for reproduction. If reproduction does takes place, the calf has a low probability of survival (Pardo).

Environmental problems also add to the decline in the dolphin population. In China, the waters are heavily polluted with pesticide DDT, a chemical banned almost in every region of the world, and toxins used in the production of plastics. These chemicals lodge in the dolphins’ body fat and are passed to baby dolphins in their mother’s milk (Parsons). Several autopsies were taken when the population declined; it was found that a 150-PPM of toxins was found, as well as high levels of mercury, lead and cadmium (Parsons). These dolphins are filled with so much toxic waste, they’re bodies are not being able to fight off all of the toxins on their own, so their losing the fight to survive. It is believed that at the rate these dolphins are dying, they will be extinct within another 5 years (Parsons). This is just one example of what is occurring in the ocean because of pollution. If we would combine all the incidents occurring all over the globe, pollution alone would be a major threat to the dolphin society. Yet, there is still exploitation occurring, adding to the decline of the population. If there are not special measures taken to save the dolphins, besides false advertisement of "dolphin safe" tuna, the entire society of the dolphin will be extinct.



Bologa. Black Sea Dolphins Face Extinction web-site:

Bryant, Peter J. Whaling and Fishing. Biology 65: Biological Conservation Lecture notes.

Everette, Bill. EXP—Dying Dolphins web-site:

Gomez, Carla P. Philippine Daily Inquire web-site:

Kelly, Dennis L. The Population Biology of the Bottlenose Dolphin along the Coast of Orange County, Southern California.

Nunez, Eric. Dolphin Kills and the Declaration of Panama web-site:

Pardo, Nina. Dolphin slaughter in Peru web-site: