Harbour porpoise (Northwest Atlantic population) COSEWIC assessment and status report: chapter 5
Species information
Name and classification
The accepted scientific name of the harbour porpoise is Phocoena phocoena (Linnaeus 1758). The English and French common names are harbour porpoise and marsouin commun, respectively, although the species may be referred to as pourcil along the northern shore of the Gulf of St. Lawrence (Laurin 1976). Geographical variation in mitochondrial haplotype frequencies and cranial morphology supports the designation of several subspecies (Read 1999). The subspecies present along the Atlantic coast of Canada is P. p. phocoena; the subspecies present on the Pacific coast is P. p. vomerina.
Description
Harbour porpoises are among the smallest cetaceans and, in eastern Canada, few individuals exceed 1.7 m in total length. The species is sexually dimorphic. In the Bay of Fundy, females reach approximately 160 cm and 65 kg, compared to 145 cm and 50 kg for males (Read and Tolley 1997). A similar dimorphism is found in Newfoundland, where female porpoises reach lengths and masses of 156 cm and 62 kg while males attain lengths and masses of 143 cm and 49 kg (Richardson 1992).
Like all phocoenids, harbour porpoises possess rounded heads that lack an external rostrum or beak. Their stocky bodies taper to a laterally flattened keel just anterior to the flukes. A small, triangular dorsal fin is located at approximately the middle of the back. The leading edge of the fin is lined with small, raised protuberances, known as tubercules. The relatively small, pointed flippers are located behind and below the angle of the mouth.
Koopman and Gaskin (1994) provide a detailed description of the pigmentation pattern of this species. A black cape extends over the dorsal and lateral surfaces, although its extent varies considerably among individuals and populations. The flanks are mottled grayish white, fading to almost white ventrally. Individuals may exhibit dark eye, chin, and lip patches. Single or multiple dark stripes may extend from the angle of the mouth to the anterior insertion of the flippers.
Figure 1. A harbour porpoise being released from a herring weir in the Bay of Fundy, Canada
Photo courtesy Grand Manan Whale and Seabird Research Station.
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