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Mammalian Species DISCLAIMER 
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Porpoises
Canada's smallest cetaceans are the harbor porpoise (Phocoena phocoena) and Dall's porpoise (Phocoenoides dalli). Although related to each other and of similar body length (maximum of 2.0-2.2 m), the two species differ in many important respects. Dall's porpoise is a chunkier, heavier animal than the harbor porpoise; its well defined, black-and-white markings are in sharp contrast to the drabber pigmentation of the harbor porpoise. Moreover, Dall's porpoise is a high-speed swimmer, known to dart back and forth across the bow of fast-moving vessels and to make distinctive splashes of seawater as it charges along the surface, to breathe. The harbor porpoise usually behaves more cryptically. It does not bow-ride and usually surfaces with little splash; thus, in all but the calmest of seas, the harbor porpoise can be hard to detect. The distribution of the two species also differs. Dall's porpoise is found only in the temperate to subarctic North Pacific. It is a deepwater animal and usually comes close to the coast only in areas where canyons or deep channels provide suitable inshore habitat. Sightings are especially common in Hecate Strait, Queen Charlotte Strait, Juan de Fuca Strait, and exposed seaways like Queen Charlotte Sound, Dixon Entrance, and Fitzhugh Sound. Dall's porpoises eat squid, crustaceans, and many kinds of fish. The harbor porpoise inhabits both the North Pacific and North Atlantic, where it ranges regularly into bays and estuaries and over offshore banks. It eats mainly squid, herring, mackerel, and other schooling, nonspiny fishes. Harbor porpoises are especially abundant in the lower Bay of Fundy, where a team of researchers from the University of Guelph (Ontario) has been studying details of their behaviour, ecology, and physiology for more than 10 years. Boaters in British Columbia sometimes report sightings of "baby killer whales" which prove, on closer examination, to have been Dall's porpoises. The killer whale is certainly found in the same areas as the similarly marked Dall's porpoise and the harbor porpoise, and it is known to attack both of them. In the Bay of Fundy and Gulf of Maine on the east coast, harbor porpoises are also preyed upon frequently by large sharks, including the great white shark (Carcharodon carcharias). Both these porpoises may have a high metabolic rate, which would mean they are extremely active and require relatively large amounts of food at frequent intervals. Several European institutions have successfully maintained, and even trained, harbor porpoises in captivity, but in North America attempts to do so have been unsuccessful. The few Dall's porpoises brought into captivity in California have proven to be high-strung and difficult to keep alive. Because of their near shore distribution, both harbor porpoises and Dall's porpoises were traditional targets of Indian hunters, who relished porpoise meat. During the nineteenth century the Micmac Indians of western Nova Scotia carried on a commercial porpoise fishery in the Bay of Fundy. Harbor porpoises were shot with shotguns and retrieved with long-handled hooks. Their blubber was rendered down, then sold in barrels at Halifax and Saint John for the soapmaking industry. Local fishermen in the Gulf of St. Lawrence and in parts o New un land and Labrador still hunt harbor porpoises for domestic consumption, and some hunting for meat is still done in the Bay of Fundy by the Passamaquoddy tribe living in Maine on the shores of Passamaquoddy Bay. At one time, harbor porpoises were hunted in the vicinity of Deer Island, New Brunswick, to supply food for ranch mink. Harbor porpoises and Dall's porpoises, as well as other related species of phocoenids worldwide, face another threat in addition to natural predators and human hunters: many die in fishing gear intended to catch fish rather than porpoises. Each year, a number of harbor porpoises become trapped in herring weirs along the coasts of New Brunswick and Nova Scotia. In the Gulf of St. Lawrence and along the coast of Newfoundland and various parts of the North American west coast, gilinets, cod and salmon traps, mackerel nets, trawls, and purse seines take their toll of harbor porpoises. The Japanese high-seas gillnet fishery for salmon in the North Pacific kills several thousand Dall's porpoises annually, as they become fatally entangled alongside sea lions, fur seals, seabirds, salmon, and many other marine organisms, in walls of netting several km long and about 6 in deep. A crude estimate of the number of harbor porpoises present during summer in the approaches to the Bay of Fundy is 4,000, with a further 2,000 distributed in coastal waters of the Scotian Shelf. These porpoises are probably part of a stock whose winter range extends south along the U.S. coast to North Carolina and offshore to Georges Bank. There are no population estimates for harbor porpoises on the west coast. The aggregate population of Dall's porpoise in the North Pacific is probably close to a million. However, the degree to which coastal stocks intermingle with pelagic stocks is unknown. |
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SOURCE: Communications Directorate Department of Fisheries and Oceans Ottawa, Ontario K1A 0E6 © Minister of Supply and Services, Canada Cat. No.: Fs 41-33/59-1988E ISBN: 0-662-16501-2 Reprinted 1993 |
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