Finless Porpoise, Neophocaena phocaenoides

The finless porpoise (Neophocaena phocaenoides) can be found in the coastal waters of Asia. Its range includes China, Indonesia, Korea, India, Japan, and Bangladesh. Its western range extends from the coast if India to the Persian Gulf and a distinct freshwater subspecies resides in the Yangtze River. It prefers to reside in shallow areas along the shore, at depths of up to 160 feet. This population is isolated within its range. A few individuals have been found as far as 99 miles off the coast of East China and the Yellow Seas, but these waters are still considered shallow. Another subspecies, N. p. sunameri, can be found in narrow range that extends from Taiwan to the East Sea/Sea of Japan.

The finless porpoise can reach an average body length of 5 feet, with an average weight between 65 to 100 pounds. Adults are completely grey in color. This species does not have a dorsal fin, the trait from which it derived its common name, instead growing a thick ridge along its back. It does not display the same behaviors that dolphins do, preferring to swim without aerial shows.

However, the N. p. phocaenoides subspecies is known to jump out of the water and preform tail stands. Although the species is not active out of the water, it is thought to be a strong swimmer and will move quickly underwater. It often swims just below the surface, rolling to one side while surfacing to breath. This action is not often seen above the surface because it does not displace much water. After breaching the surface, this species will only take three or four short breaths before diving again and will not resurface near the previous area.

The finless porpoise is most commonly found in alone, single pair groupings, and in groups of up to twelve individuals. Groups of up to fifty individuals have been seen. A typical group consists of two adults and one mother and calf pair. Groupings of three or more individuals consist of these individuals and possibly single individuals. There is no social hierarchy within the groups, and the only stable relationships are displayed between a mother and her calf.

The diet of the finless porpoise varies slightly depending upon its location. In the Yangtze River, the N. p. phocaenoides subspecies consumes shrimp and fish, while the population found in Yellow Sea area consumes shrimp, fish, and squid. The population found in Japanese waters consumes shrimp, fish, octopuses, and cuttlefish. This species is known as an opportunistic feeder and it will consume whatever is available at any given time. Individuals living in estuaries, rivers, and mangroves will consume plant materials like rice and leaves, as well as eggs that have been left on vegetation.

The breeding season for the finless porpoise occurs between late spring and early summer. Females have a pregnancy period between ten and eleven months, after which one calf is born. The calf will cling to its mothers by latching onto the raised area of the back. Calves are born black in color with a grey underbelly, but will grow into their adult color between four and ten months. Calves are weaned between six and fifteen months. Males reach sexual maturity between four to six years of age, while females breed later in life at around nine years of age.

The total population number of the finless porpoise is not known.  However, by comparing the result of two studies conducted in the 1970’s and between the years of 1999 to 2000, experts have found that its numbers are declining. These studies have also shown a decline in habitat, and it is thought that these deteriorations have been occurring over a span of decades. In 2006, one study showed that there were less than 400 individuals in the Yangtze River. In the same year, it was estimated that between 700 and 900 individuals resided in the river, with a total population of 1,400 individuals in all Chinese waters including 500 in the Dongting and Poyang Lakes. As of 2007, it was found that the population numbers had declined by more than half since 1997, with a yearly decline of 7.3 percent.

One threat to the finless porpoise is sand dredging, which has become a lucrative industry in many areas, including the region that borders the Poyang Lake. Dredging muddies the water in the lake, making visibility difficult for the porpoises, causing them to rely mostly on their sonar abilities to find food and move around. Despite the efficiency of this species’ sonar, the boats that enter and leave the lake make it difficult for the dolphin to hear. Every minute two boats will enter and leave the lake, causing movement for this porpoise to be difficult. Other threats including becoming trapped in gillnets and other human caused problems, although its main threat is habitat loss.

Conservation efforts that are currently being conducted occurred while efforts to save the baiji were being conducted, but this species is near extinction. During this time, five finless porpoises were captured and transported to Tian-e-Zhou Oxbow Nature Reserve, where a small population of 28 individuals now reside in a lake in that area. It has been protected in Awajima Island, Takehara since 1930, and this protection has now been extended into all Japanese coastal areas.  It appears in Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals (CMS), which states it an unfavorable status that requires more research and conservation efforts. The finless porpoise appears on the IUCN Red List with a conservation status of “Vulnerable.”

Image Caption: Finless Porpoise at Miyajima Aquarium, Japan. Credit: ori2uru/Wikipedia (CC BY 2.0)