Aquatic Species at Risk - Harbour Porpoise - Northwest Atlantic

At a glance

One of the smallest of whales, the harbour porpoise is found primarily over continental shelves in Canada in two populations: the Pacific and the northwest Atlantic. However, as its name suggests, this timid creature is sometimes found in bays and harbours, particularly during the summer. Threats to the northwest Atlantic harbour porpoise population include accidental entanglement in commercial fishing nets.

About the northwest Atlantic harbour porpoise

Harbour porpoises average just 1.6 metres in length and weigh about 50 kg. Well adapted to cold water, they are rarely found in water warmer than 16°C. They can live in large groups but more often stay in small pods of less than 10 animals, and most often as single animals. Females tend to be larger than the males, and both genders live relatively short lives: few harbour porpoises live to 20 years.

Female harbour porpoises become sexually mature at three years of age. After mating in early summer and following a gestation period of 10 to 11 months, females give birth to calves that nurse for at least eight months. As female harbour porpoises tend to become pregnant each year, for most of their adult lives they are pregnant with new offspring while nursing another calf. Harbour porpoises feed on small fish such as cod, herring, hake, capelin and sand lance.

How to recognize the northwest Atlantic harbour porpoise

The harbour porpoise has a noticeably rounded head that lacks an obvious beak or snout. It has a small, triangular dorsal fin that sits approximately in the middle of its back. Their sides are mottled grayish-white, which becomes almost fully white on their bellies. It looks like they wear a black ‘cape’ over their backs and sides, but the look of the cape varies quite a bit among individuals. Northwest Atlantic harbour porpoises also may have dark patches on their faces. Males and females usually look the same in terms of colour, but young porpoises are typically darker.

Ari S. Friedlaender


Jeffrey C. Domm

Where the northwest Atlantic harbour porpoise lives

Northwest Atlantic harbour porpoises are spread out over the northern hemisphere’s continental shelves (the shallower coastal areas of the ocean, generally within 250 kilometres of shore). But as their name implies, they are often sighted close to shore, seeking out harbours and bays -- especially in summer months. In Canada, the northwest Atlantic harbour porpoise ranges from the Bay of Fundy north to northern Labrador, with three distinct populations in Newfoundland-Labrador, the Gulf of St. Lawrence and the Bay of Fundy/Gulf of Maine. These groups regularly travel down to American waters and back to Canada.

Why it's at risk

The northwest Atlantic harbour porpoise’s most significant threat may be getting caught in bottom-set gill nets intended to capture groundfish such as cod. Other threats to this species include habitat degradation, and loss of habitat due to acoustic harassment devices used by commercial fish-farmers (i.e., salmon producers) to deter natural predators away from their stocks. Northwest Atlantic harbour porpoises are also at risk from environmental contamination by pesticides and other chemicals such as polychlorinated biphenyls (PCBs).

What's being done

The northwest Atlantic harbour porpoise is now under consideration for addition to the federal Species at Risk Act (SARA) as a species of special concern. The harbour porpoise is protected under the federal Fisheries Act which prohibits destruction of fish habitat and under the Marine Mammal Regulations of this Act. The harbour porpoise is also on the IUCN (World Conservation Union) Red list of Threatened Animals, and is included in the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), which reduces commercial exploitation of species at risk.

Harbour porpoises trapped in the Bay of Fundy by herring weirs, or herring fish-traps, have been routinely freed and released. In addition, the gillnet ground-fishery has made various efforts to minimize its impact on the harbour porpoise. Other measures to reduce bycatch are being investigated and could include the use of acoustic deterrents or modified gear, such as barium sulfate coated fishing-nets -- which could give harbour porpoises and other marine mammals an early warning signal of the danger of nets along their swimming route.

As well, the Trans North Atlantic Scans Survey, scheduled for 2007, will (among other things) allow DFO to estimate the number of harbour porpoises in Canadian waters. Furthermore, the distribution of porpoises in Newfoundland is being monitored with underwater acoustic equipment.

What can you do?

Northwest Atlantic harbour porpoises will get the protection they need only if all Canadians work together to reduce threats. Find out more about the northwest Atlantic harbour porpoise, and do your best to reduce threats wherever possible to better protect the northwest Atlantic harbour porpoise’s critical habitat. Get involved with the Habitat Stewardship Program for Species at Risk(HSP) or another conservation organization.

Background information provided by Environment Canada a, March 2006.