The harbour porpoise, also known as the common porpoise, is a small cetacean with a rotund, stocky body that tapers toward the tailstock. This porpoise reaches a maximum length of 1.9 m (6 ft) and maximum weight of 90 kg (198 lbs). On average, harbour porpoises are smaller, and do not exceed 1.5 m (5 ft) or weigh more than 60 kg (132 lbs). The females are slightly larger than the males. This porpoise has no beak, but a blunt, rounded snout is present. There are 22–28 small, spade-shaped teeth on each side of the upper jaw and 22–26 on each side of the lower jaw. The harbour porpoise is dark gray or dark brown on the dorsal side, lighter gray on the flanks, and white on the ventral side. The flippers are also dark in colour with a dark stripe that extends to the eye. The flippers are small, oval, and rounded at the tips. The low, wide dorsal fin is triangular in shape and found slightly behind the center of the body. In some individuals, small nodules are found on the leading edge of the dorsal fin. The flukes are small and curved, and have a median notch. Harbour porpoises are found singly, in pairs, or in small groups of 6–10 animals, however larger groups between 50–100 animals have been observed feeding. The harbour porpoise is often found stranded, which is likely due to its preferred shoreline habitat. Although some live stranded porpoises have been taken to aquariums, few survived in captivity. This porpoise is a non-gregarious species that shies away from boats. They are often detected by the loud puffing sound they make as they surface to breathe.
World Range and Habitat
The harbour porpoise is found in shallow, coastal waters of the North Atlantic, North Pacific, and Black Sea in temperate and sub-arctic waters of less than 15 Celsius (60 F). They sometimes swim into bays and large rivers.
The harbour porpoise, feeds on fishes such as cod, herring, pollock, sardines, and whiting, anchovies, and on squid. This porpoise consumes about 10% of its body weight each day.
Harbour porpoises reach sexual maturity at 3–4 years. Calves are born 70–90 cm (3 ft) in length 6.4–10kg (22 lbs) in weight following a gestation period of about 11 months. Females give birth about every two years, and nurse for about eight months.
Warnings and Comments
Because of its near-shore habitat, the harbour porpoise has been widely hunted for oil and meat. Although they are still abundant throughout their range, populations have declined. They are at-risk of entanglement in salmon and cod nets in the eastern North Atlantic; and in trawl and gill nets in the Pacific. In the Baltic and Black seas, populations have declined due to drive fisheries. These porpoises are also at risk of pollution from pesticides, destruction of habitat by coastal development, and marine traffic.