Harbour Porpoise

Harbour Porpoise

Marsouin commun

Phocoena phocoena


Length

1.5 to 2 m

Weight

45 to 50 kg, up to 65 kg

sociability

Sometimes solitary or in pairs, but usually in groups of 5 to 10

Longevity

10 to 13 years

Dive time

1 to 3 min, up to 12 min

Observations

Regular in the Gulf and in the Estuary

Worldwide distribution

Coastal waters of the Northern Hemisphere

Worldwide population

Unknown, probably in decline

Status

Special Concern



Other names: Common Porpoise, Puffing Pig, Puffer




Short, but intense lives!

Harbour porpoises are the smallest of the St. Lawrence cetaceans, and those with the shortest lifespan. They appear to live in a perpetual state of urgency and performance, with one predominant motivation for both genders: reproduction.


Population, range and habitat:

In the St. Lawrence: Harbour porpoises visit coastal areas of the Gulf and Estuary during summer, from late June to the end of September. They can often be found in fjords, bays, estuaries and, of course, harbours. The Gulf of St. Lawrence population is estimated at over 20 000 head.

Migration: Its winter habitat is not well known. It appears to move offshore in order to avoid ice. According to a 1970s study on accidental entanglement, some harbour porpoises winter-over in the Estuary.

Worldwide: The harbour porpoise occupies the coastal temperate and sub-Arctic waters of the Northern Hemisphere. The western North Atlantic population is divided into four sub-populations: Gulf of St. Lawrence, Bay of Fundy-Gulf of Maine, Newfoundland-Labrador and Greenland. It is also present in the North Pacific. There is even a population living in the Black Sea, an inland body of water bordered by several Eastern European countries, Russia and Turkey and another in the Azov Sea, a branch of the Black Sea.


Behaviour:

Feeding: The harbour porpoise hunts small, schooling fish such as capelin, herring, pollock and mackerel within the water column. It also feeds on benthic crustaceans and squid.

At the surface: Its rapid swimming movement gives one the impression that it is rolling at the surface. Its sonorous blow is only audible on calm days. It swims slowly, but can cover great distances in a single day. Harbour porpoises sometimes remain immobile for several seconds at the surface before diving. They rarely leap out of the water. Harbour porpoises are timid and are not often curious about boats.

While diving: They generally dive for less than five minutes at a time to depths of 15 to 30 m. The deepest recorded dive for a harbour porpoise is 226 m.

Social behaviour: The harbour porpoise is a gregarious animal. It lives in small groups of two to five that sometimes gather into herds of several dozen to several hundred at a time. These gatherings are clearly food related. Highly mobile, harbour porpoises can range over vast territories of thousands of square kilometres.

Vocal behaviour: They emit repetitive clicks and low-pitched sounds to communicate and for echolocation purposes.


Reproduction:

Males attain sexual maturity at three to four years of age, while females become sexually mature between two and four. The male reproductive strategy is based on sperm competition, for which they are very well equipped. Their testicles can grow to an impressive size during the mating season, attaining four to seven percent of their body weight or 3.2 kg for a 44.6 kg animal. Success goes to the one who produces the most sperm and is able to mate repetitively with the same female or with several different females. Mating takes place in July and August. Gestation lasts approximately 10 months. Births take place in spring and early summer, peaking in June. Nursing lasts from eight to 12 months. Female harbour porpoises are among the rare cetaceans that can calve on an annual basis. This implies that they are gestating and lactating simultaneously for a large portion of their adult lives… an enormous physiological investment!


About scientific research:

Its coastal habits and our fishing methods do not go well together. Thousands of incidents of accidental entanglement involving gillnets in the early 1990s caused researchers to be concerned for the population’s very survival. Death rates appear to have declined in the St. Lawrence since the cod-fishing ban of 1993. However, according to the work of Fisheries and Oceans Canada’s Véronique Lesage, this threat could still affect population recovery.


Harbour porpoise "Science and conservation" page