By Nadine Pinnell, Cara Lachmuth, and Doug Sandilands
Harbour porpoises (Phocoena phocoena), already one of the shiest cetaceans in British Columbia, could become even harder to find in the future.
In November 2003, COSEWIC (the Committee on the Status of Endangered Wildlife in Canada) identified the North Pacific harbour porpoise population as a species of ‘Special Concern’. This designation recognizes that the population is particularly sensitive to human activities or natural events, although it is not in immediate danger of extinction. Prior to this, harbour porpoises in the Pacific had been listed as “Data Deficient”, indicating that not enough information was available to determine their status. In July 2004, COSEWIC will pass its assessment of the Pacific harbour porpoise population on to the Minister of the Environment, starting the process of adding the population to the federal List of Wildlife Species at Risk.
If harbour porpoises in the Pacific are legally added to the Species at Risk Act (SARA), the government is required to develop a management plan that includes specific measures for the conservation of the population and their habitat within three years. More information about the listing process.
Harbour porpoise biology
With a maximum length under 2 metres, harbour porpoises are the smallest cetaceans found on the B.C. coast. Their small size, dark grey to brown coloration, and inconspicuous behaviour can make them hard to spot. They swim slowly and rarely leap out of the water so their small dark triangular dorsal fin is often the only feature visible to observers. Unlike dolphins and other porpoises, harbour porpoises tend to be quite shy, rarely approaching or bow riding near boats. Nicknamed “puffing pigs” in eastern Canada, boaters will sometimes hear them before they see them as the sharp puffing sound of their breath, which sounds like a sneeze, is quite distinctive.
Globally, harbour porpoises occur mainly over continental shelves in temperate waters of the northern hemisphere, seldom inhabiting water warmer than 16°C. As their name suggests, they prefer shallow inshore areas such as bays, estuaries, and harbours, typically inhabiting waters less than 200 m in depth.
Harbour porpoises feed on a variety of small (10-25 cm) fish and squid, which they catch both within the water column and from the ocean floor. In British Columbia, prey species include schooling fishes and squid such as Pacific herring (Clupea pallasi), Pacific hake (Merluccius productus), market squid (Loligo opalescens), and blackbelly eelpout (Lycodopsis pacifica). It has been suggested that the distribution of harbour porpoises in Atlantic Canada could be related to the distribution of the schooling fish they eat, which may also be true for harbour porpoises in the Pacific. Their small size limits the amount of energy they can store in their blubber, which means that they must stay close to their prey sources in order to get all of the energy they need to stay warm in the cooler waters they prefer.
In contrast with dolphins and other porpoises, harbour porpoises are fairly solitary animals that generally travel in groups of one to three individuals. They can occasionally be found in larger groups, although most researchers think these aggregations are the result of a number of smaller groups or individuals congregating in an area to take advantage of a particularly rich food source rather than for social reasons. For example, a recent report to the B.C. Cetacean Sightings Network described a large group of 15-20 porpoises feeding in the same area, with several smaller groups of 3-4 individuals distinguishable within the larger group.
Harbour porpoises are short-lived for cetaceans, with an average lifespan of under fifteen years. Males and females mature sexually between three and five years of age. Once mature, most females will have a single calf between May and September every 1-2 years. As harbour porpoises have a gestation period of 11 months followed by an eight month period of nursing for each calf, females can spend much of their lives pregnant with one calf while nursing the calf of the previous year. Mating occurs during the late summer and early fall of each year, at which point the testes of male harbour porpoises enlarge to comprise up to 6% of their total body weight. Little is known about the social structure of harbour porpoises. Anna Hall, a graduate student studying harbour porpoises in southern British Columbia, observed that groups of two adults and a calf were common, especially in the summer and early fall months. It is possible that these could be family groups of some type. In any case, the social structure of harbour porpoises does not seem to be as complex as that of some other cetacean species (eg. resident killer whales).
The main natural threats to harbour porpoises in BC are transient killer whales (Orcinus orca). White sharks (Carcharodon carcharias) and other shark species may also take harbour porpoises in BC waters. Unfortunately, as the ‘Special Concern’ designation indicates, humans and human-related activities such as coastal development pose a number of additional threats to harbour porpoises. They are prone to becoming entrapped and killed in fishing nets, can be displaced from areas by underwater noise and human presence, and could be affected by contaminants in their food chain resulting from marine pollution.
To learn more about threats to harbour porpoises, please see the follow-up story “Threats facing the Pacific harbour porpoise population”.
How can I help reduce threats to harbour porpoises?
1. Let us know if you see a harbour porpoise. Watch for small, dark, triangular dorsal fins that surface smoothly the next time you’re out on the water. Remember that harbour porpoises generally do not lift their bodies out of the water, tend to travel alone or in pairs, and are small, dark cetaceans. By reporting your sightings of harbour porpoise or any other type of cetacean, you are gathering information that will help identify important habitat areas and give these species the protection they need.
2. If you do see a harbour porpoise while out on the water, observe the Be Whale Wise guidelines: slow down, don’t approach closer than 100 metres, and avoid approaching it from the front or behind.
3. If you see a harbour porpoise (or any other cetacean) entangled in fishing gear or other debris, call Fisheries and Oceans Canada at 1-800-465-4336. They will be able to call upon experts such as those at the Vancouver Aquarium to help disentangle the porpoise.
4. Make sure that all of your lines, nets, and other gear are properly stowed when you are out on the water so that they cannot pose a hazard to cetaceans or other marine organisms. If you see discarded netting or abandoned fishing gear adrift and you are able to safely access it, please remove it from the water and discard it properly on land.
5. Help reduce the number of toxins entering the ocean and contaminating the marine environment. Avoid using bleached paper and pesticides and make sure oil and household toxic waste products are disposed of properly.
Baird, R.W. 2003. Update COSEWIC status report on the harbour porpoise Phocoena phocoena (Pacific Ocean population) in Canada. Committee on the Status of Endangered Wildlife in Canada, Ottawa. 1-22 pp. [PDF]
Baird, R.W. and T.J. Guenther. 1995. Account of harbour porpoise (Phocoena phocoena) strandings and bycatches along the coast of British Columbia. Reports of the International Whaling Commission Special Issue 16:159-168. [abstract]
COSEWIC 2003. COSEWIC assessment and update status report on the harbour porpoise Phocoena phocoena (Pacific Ocean population) in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vi + 22 pp. [PDF]
Hall, A.M. 2004. Seasonal Abundance, Distribution and Prey Species of Harbour Porpoise (Phocoena phocoena)in Southern Vancouver Island Waters. M.Sc. thesis. University of British Columbia, Vancouver, BC. 109 pp. [PDF]