Harbour Porpoise (Phocoena phocoena)
– a maximum length of 1.8 metres and average adult length is 1.6 metres (smallest cetacean in BC)
– dark brown to gray, lighter colour on the belly
– distinct line from mouth to top on pectoral fin
– triangular, same colour as body
– does not bring body completely out of the water
– more of a solitary animal than the Dall’s
– tend to avoid boats.
– normally travels alone or in small group sizes (up to 3)
– occasionally in the spring, large aggregations of 100 or more are seen
– when surfacing, dorsal fin appears to rotate as on a wheel.
Can Be Confused With
– Dall’s porpoise
Harbour porpoise have a circumpolar distribution throughout the temperate and boreal waters of the northern hemisphere. Three isolated groups are recognized: north Pacific, north Atlantic, and Black Sea- Sea of Azov. They prefer near coastal waters although occasional sightings in deep water are recorded (see map below). They are frequently seen in BC’s many inlets and fjords. Infrequently, they may also be spotted in brackish rivers.
Harbour porpoise are thought to remain resident for extended periods in one area. They are a very difficult animal to spot and individually identify due to their small dorsal fin, cryptic behaviour, and minimal surface activity.
Harbour porpoises are generally seen in small groups between 1 to 3 animals. Larger congregations of several dozen harbour porpoises are sometimes observed, particularly in spring or fall. These large groups are thought to be feeding on prey that is concentrated by strong, seasonal tides. Harbour porpoise feed on small schooling fishes, such has herring, eelpouts, hake, sandlance, salmon and cod, as well as squid. Calves may also feed on euphasiids between weaning and when they commence eating fish.
Male and female harbour porpoises look similar, and while females often are slightly larger, it is difficult to tell the two sexes apart. Harbour porpoises are often described as promiscuous and polyandrous with significant sperm competition. Males have a marked development of the testes seasonally, which may weigh up to 6% of their body weight during the mating season. In British Columbia, mating appears to peak in late summer to early fall. Females are pregnant for 7 to 11.4 months. A single calf is born mainly from May to September. Nursing may occur for up to 8 to 12 months, but is significantly reduced after the first few months. It is unknown when harbour porpoises reach sexual maturity in the north Pacific, but in the north Atlantic it is around 3-4 years. Females have a calf every 1 to 2 years, and both sexes may live to 13 years.
Hybridization between Dall’s porpoise and harbour porpoise occurs occasionally in BC waters with harbour porpoise as the paternal parent and Dall’s porpoise as the maternal parent. Hybrids tend to appear more similar to Dall’s porpoise in body shape, diving characteristics and behaviour, but they lack the white side patches and the colouring is more similar to the harbour porpoise.
Transient (mammal-eating) killer whales and sharks may prey on harbour porpoises, although evidence of the latter has only been observed once in British Columbia. Harbour porpoises are the most frequently reported stranded cetacean in British Columbia though reasons for their stranding are various. In many parts of their range, harbour porpoise populations are heavily impacted by entanglement in fish nets, particularly gillnets. They also appear to very sensitive to noise and other human impacts in more urban areas.
STATUS IN CANADA
COSEWIC: Special Concern (2003)
Reason for Designation: They appear to be particularly sensitive to human activities, and are prone to becoming entrapped and killed in fishing nets. They are a short lived shy species that are now rarely seen at the highly developed areas of Victoria and Haro Strait. Continued development and use of its prime habitat by humans are some of the main threats. They are displaced by underwater noise, and could be affected by contaminants in their food chain.
BC Provincial Red List: Blue (have characteristics that make them particularly sensitive or vulnerable to human activities or natural events.)