Research history In
Aristotle's time, the 4th century BCE, porpoises were regarded as fish due to their superficial similarity. Aristotle, however, could already see many physiological and anatomical similarities with the terrestrial vertebrates, such as blood (circulation), lungs, uterus and fin anatomy. His detailed descriptions were assimilated by the Romans, but mixed with a more accurate knowledge of the dolphins, as mentioned by
Pliny the Elder in his "Natural history". In the art of this and subsequent periods, porpoises are portrayed with a long snout (typical of dolphins) and a high-arched head. The
harbour porpoise was one of the most accessible species for early
cetologists, because it could be seen very close to land, inhabiting shallow coastal areas of Europe. Much of the findings that apply to all cetaceans were first discovered in porpoises. One of the first anatomical descriptions of the airways of the whales on the basis of a harbor porpoise dates from 1671 by John Ray. It nevertheless referred to the porpoise as a fish, most likely not in the modern-day sense, where it refers to a zoological group, but the older reference as simply a creature of the sea (cf. for example
star-fish,
cuttle-fish,
jelly-fish and
whale-fish).
In captivity in captivity Harbour porpoises have historically been kept in captivity, under the assumption that they would fare better than their dolphin counterparts due to their smaller size and shallow-water habitats. Up until the 1980s, they were consistently short-lived. Harbour porpoises have a very long captive history, with poorly documented attempts as early as the 15th century, At least 150 harbour porpoises have been kept worldwide, but only about 20 were actively caught for captivity. while the third (mother of first born in captivity) is the world's oldest known harbour porpoise, being 31 years old in 2026. The typical age reached in the wild is 14 years or less. Very few harbour porpoises have been born in captivity. Historically, harbour porpoises were often kept singly and those who were together often were not mature or of the same sex. In addition to the few kept in Europe, harbour porpoise were displayed at the
Vancouver Aquarium (Canada) until recently. This was a female that had beached herself onto
Horseshoe Bay in 2008 and a male that had done the same in 2011. They died in 2017 and 2016 respectively. Finless porpoises have commonly been kept in Japan, as well as China and Indonesia. As of 1984, ninety-four in total had been in captivity in Japan, eleven in China, and at least two in Indonesia. As of 1986, three establishments in Japan had bred them, and there had been five recorded births. Three calves died moments after their birth, but two survived for several years. The reopened
Miyajima Public Aquarium (Japan) houses three finless porpoises. As part of an attempt of saving the
narrow-ridged (or Yangtze) finless porpoise, several are kept in the Baiji Dolphinarium in China. After having been kept in captivity for 9 years, the first breeding happened in 2005. Small numbers of Dall's porpoises have been kept in captivity in both the United States and Japan, with the most recent being in the 1980s. The first recorded instance of a Dall's taken for an aquarium was in 1956 captured off
Catalina Island in southern California. Dall's porpoises consistently failed to thrive in captivity. These animals often repeatedly ran into the walls of their enclosures, refused food, and exhibited
skin sloughing. Almost all Dall's porpoises introduced to aquaria died shortly after, typically within days. Only two have lived for more than 60 days: a male reached 15 months at
Marineland of the Pacific and another 21 months at a
United States Navy facility. The first and only caught for captivity were two females in 2017. Both became distressed and were rapidly released, but one of them died in the process. Soon after the project was abandoned.
Threats Hunting by lancing in
Bay of Fundy Porpoises and other smaller cetaceans have traditionally been hunted in many areas, at least in Asia, Europe and North America, for their meat and blubber. A dominant hunting technique is drive hunting, where a pod of animals is driven together with boats and usually into a bay or onto a beach. Their escape is prevented by closing off the route to the ocean with other boats or nets. This type of fishery for
harbour porpoises is best documented from the
Danish straits, where it occurred until the end of the 19th century (it was banned in 1899), and again during the shortages in
World War I and
World War II. The
Inuit in the Arctic hunt harbour porpoises by shooting and drive hunt for
Dall's porpoise still takes place in Japan. The number of individuals taken each year is in the thousands, although a quota of around 17,000 per year is in effect today making it the largest direct hunt of any
cetacean species in the world and the sustainability of the hunt has been questioned.
Fishing swimming in the
Gulf of California. Porpoises are highly affected by
bycatch. Many porpoises, mainly the
vaquita, are subject to great mortality due to
gillnetting. Although it is the world's most endangered marine cetacean, the vaquita continues to be caught in small-mesh gillnet fisheries throughout much of its range. Incidental mortality caused by the fleet of El Golfo de Santa Clara was estimated to be at around 39 vaquitas per year, which is over 17% of the population size. Harbour porpoises also suffer drowning by gillnetting, but on a less threatening scale due to their high population; their mortality rate per year increases a mere 5% due to this. The fishing market, historically has always had a porpoise bycatch. Today, the
Marine Mammal Protection Act of 1972 has enforced the use of safer fishing equipment to reduce bycatch.
Environmental hazards Porpoises are very sensitive to
anthropogenic disturbances, and are
keystone species, which can indicate the overall health of the marine environment. Increasing pollution is a serious problem for marine mammals. Heavy metals and
plastic waste are not biodegradable, and sometimes cetaceans consume these hazardous materials, mistaking them for food items. As a result, the animals are more susceptible to diseases and have fewer offspring. Harbour porpoises from the
English Channel were found to have accumulated heavy metals. This effect, of course, only occurs in porpoises that dive to great depths, such as Dall's porpoise. Additionally, civilian vessels produce sonar waves to measure the depth of the body of water in which they are. Similar to the navy, some boats produce waves that attract porpoises, while others may repel them. The problem with the waves that attract is that the animal may be injured or even killed by being hit by the vessel or its propeller.
Conservation The harbour porpoise, spectacled porpoise, Burmeister's porpoise, and Dall's porpoise are all listed on Appendix II of the
Convention on the Conservation of Migratory Species of Wild Animals (CMS). In addition, the Harbour porpoise is covered by the
Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas (ASCOBANS), the
Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area (ACCOBAMS) and the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia. Their conservation statuses are either at
least concern or
data deficient. As of 2014, only 505
Yangtze finless porpoises remained in the main section of the Yangtze, with an alarming population density in Ezhou and Zhenjiang. While many threatened species decline rate slows after their classification, population decline rates of the porpoise are actually accelerating. While population decline tracked from 1994 to 2008 has been pegged at a rate of 6.06% annually, from 2006 to 2012, the porpoise population decreased by more than half. Finless porpoise population decrease of 69.8% in just a 22-year span from 1976 to 2000. 5.3%. A majority of factors of this population decline are being driven by the massive growth in Chinese industry since 1990 which caused increased shipping and pollution and ultimately
environmental degradation. Some of these can be seen in damming of the river as well as
illegal fishing activity. To protect the species, China's Ministry of Agriculture classified the species as being National First Grade Key Protected Wild Animal, the strictest classification by law, meaning it is illegal to bring harm to a porpoise. Protective measures in the
Tian-e-Zhou Oxbow Nature Reserve has increased its population of porpoises from five to forty in 25 years. The
Chinese Academy of Sciences'
Wuhan Institute of Hydrobiology has been working with the
World Wildlife Fund to ensure the future for this subspecies, and have placed five porpoises in another well-protected area, the He-wang-miao oxbow. Five protected natural reserves have been established in areas of the highest population density and mortality rates with measures being taken to ban patrolling and harmful fishing gear in those areas. There have also been efforts to study porpoise biology to help specialize conservation through captivation breeding. The Baiji Dolphinarium, was established in 1992 at the Institute of Hydrobiology of the Chinese Academy of Sciences in Wuhan which allowing the study of behavioral and biological factors affecting the finless porpoise, specifically breeding biology like seasonal changes in reproductive hormones and breeding behavior. Because
vaquitas are indigenous to the Gulf of California, Mexico is leading conservation efforts with the creation of the
International Committee for the Recovery of the Vaquita (CIRVA), which has tried to prevent the accidental deaths of vaquitas by outlawing the use of fishing nets within the vaquita's habitat. CIRVA has worked together with the
CITES, the
Endangered Species Act, and the
Marine Mammal Protection Act (MMPA) to nurse the vaquita population back to a point at which they can sustain themselves. CIRVA concluded in 2000 that between 39 and 84 individuals are killed each year by such gillnets. To try to prevent extinction, the Mexican government has created a nature reserve covering the upper part of the Gulf of California and the
Colorado River delta. They have also placed a temporary ban on fishing, with compensation to those affected, that may pose a threat to the vaquita. ==See also==