14. Chickadee Notes

Harbour Porpoise in New Brunswick 

Status

Harbour PorpoiseAlthough still a familiar mammal in northern seas around the world, the Harbour Porpoise, Phocoena phocoena, has declined or disappeared over significant parts of its range. There is little information available on the status of the Harbour Porpoise population off the east coast of New Brunswick in the Gulf of St. Lawrence. The only population estimates for Canadian waters encompass the Bay of Fundy-Gulf of Maine, which has an estimated population of about 45,000 animals. Harbour Porpoise may be observed in the Bay of Fundy throughout the year, but peak numbers are present in the Bay from late July to mid-September, where porpoise have been studied intensively.

Until the early part of this century the Harbour Porpoise off Grand Manan and nearby islands were shot and speared in sizable numbers by Passamaquoddy Indians. This fishery, for oil and meat, may have reduced porpoise populations locally, although it is now difficult to judge its impact. Porpoise were taken in small numbers by natives until the early 1970s.

The decline in this species is due largely to the toll exacted by incidental catches of Harbour Porpoise in fishing gear.

Since 1991 the federal-provincial Committee on the Status of Endangered Wildlife in Canada has considered the northwest Atlantic population of Harbour Porpoise threatened. The decline in this species is due largely to incidental catches of Harbour Porpoise in fishing gear, especially that of the groundfish gillnet fishery. In the Fundy region this fishery was established about 20 years ago. A few porpoise also die in fish weirs, where trapped porpoise are sometimes needlessly shot or occasionally drown. Increased human disturbance of coastal areas and contamination of the marine environment may also be involved in declining numbers of Harbour Porpoise.

The International Whaling Commission has concluded that recent levels of incidental mortality in fishing gear, especially groundfish gillnets, pose a serious threat to the Harbour Porpoise population in the Gulf of Maine-Fundy region and should be immediately reduced. There is evidence of a change in population structure and population decline in the Harbour Porpoise in the Bay of Fundy since the early 1970s. It is estimated that in addition to the small number of porpoises that die in weirs, in excess of 2,000 Harbour Porpoise are killed annually in gillnets in the Bay of Fundy-Gulf of Maine.

Natural History

The Harbour Porpoise, Phocoena phocoena, is the smallest of the cold-water marine whales and the only species of porpoise in New Brunswick waters. Harbour Porpoise average about 1.6 m in length and weigh approximately 50 kg. Females are slightly larger than males. The snout is bluntly pointed, lacking the obvious beak so characteristic of the dolphins. Areas of the flanks and under surface are white while the flippers, flukes, and upper surface are dark gray. Frequently there is a gray stripe from the eye to the anterior angle of the flipper. The dorsal fin is triangular rather than curved or sickle-shaped, and the sloped trailing edge is only slightly concave. The teeth of the Harbour Porpoise are spoon or spade-shaped, a distinctive feature of all porpoise species.

During the warmer months Harbour Porpoise inhabit inshore waters such as bays, channels, and harbours. In the lower Bay of Fundy gams, or herds, of Harbour Porpoise can be easily observed around Deer Island, Grand Manan, Campobello, and around The Wolves, a series of rocky islands near Grand Manan. Throughout the lower Bay porpoise spend the summer months feeding in small groups of up to a dozen animals before most begin to depart in late September.

There are several records of large sharks feeding on Harbour Porpoise in the Bay of Fundy.

We know little about the social structure of the Harbour Porpoise. However, there is a pattern of seasonal migration, with porpoise moving farther offshore and dispersing southward (Fundy) or eastward (Gulf of St. Lawrence) during the winter. These seasonal movements can be correlated with those of herring, the most important porpoise prey species. Harbour Porpoise also feed on a wide variety of other fish, including cod, mackerel, hake, ocean pout, gaspereau, flounder, and hagfish as well as taking squid and crustaceans.

The Harbour Porpoise is sometimes referred to as "puffing pig" because of the snuffling sounds it makes when breathing. In calm water porpoise roll leisurely, or lie motionless at the surface, exhaling with a puff and inhaling with a whine. In choppy water they move more quickly, throwing up a spray as they plunge into the waves. Rarely does the Harbour Porpoise jump. It may be surprising that a small, largely inshore species such as the Harbour Porpoise should be a relatively good diver. Although the majority of dives are under 50 m, dives to over 200 m have been recorded. Nonetheless, Harbour Porpoise rarely remain submerged for more than three to four minutes.

Although human activities are the principal threat to this species, Harbour Porpoise are not without natural predators. There are several records of large sharks feeding on Harbour Porpoise in the Bay of Fundy. On one occasion, a 907 kg White Shark was captured near Grand Manan with three Harbour Porpoise in its stomach, each porpoise severed into two or three pieces.

Harbour Porpoise give birth to a single young. Bay of Fundy porpoise births peak in mid-May, following a gestation period of 10.6 months. At birth the calf is about 80 cm in length and 6-8 kg in weight. During the first few months of life newborn porpoise are difficult to observe as they remain close to the dorsal fin of the mother. However, by autumn the calf is readily visible.

The calf grows rapidly, teeth erupting at about five months by which time it weighs about 25 kg. In the Bay of Fundy young porpoise start to take solid food during the late summer while they are still being nursed. Euphasid crustaceans are an important first prey for young Harbour Porpoise. Young are weaned at about eight months by which time they have learned to capture larger, more challenging prey such as fish.

...Harbour Porpoise rarely remain submerged for more than three to four minutes.

Harbour Porpoise in the western North Atlantic are sexually mature at three to four years of age. Mating takes place in late June and most females reproduce annually, although they may not bear their first offspring until their second or third year of sexual maturity. Although the rare individual may live 15 years, generally Harbour Porpoise do not live more than eight years. Harbour Porpoise have a slow reproductive rate with most individual females producing no more than several young during a lifetime. This, and the short breeding period in summer, has given the species little flexibility with which to respond to the increased mortality resulting from gillnet fishing.

Helping Out

Like all whales in Canadian waters, the Harbour Porpoise is protected under the Marine Mammal Regulations of the Fisheries Act, which prohibit killing or any form of disturbance. Although Harbour Porpoise generally ignore or avoid boats, whale watchers and recreational boaters should follow whale watching guidelines and always stay at least 100 m away from porpoise. More details on the procedures for whale watching are available from the federal Department of Fisheries and Oceans.

High concentrations of mercury and organochlorine hydrocarbons have been recorded in Bay of Fundy Harbour Porpoise...

It has been acknowledged that the incidental mortality of Harbour Porpoise in gillnets is unacceptable and seriously threatens porpoise populations. Although declining groundfish quotas mean fewer nets and lower incidental mortality of porpoise, the specific issue of porpoise drowning in gillnets has yet to be adequately addressed. In contrast, Harbour Porpoise which follow herring into weirs can be easily released alive, even during removal of fish (seining). Harbour Porpoise struggle little when handled but care must be taken to ensure that they are not tangled in nets and do not overheat when removed from the water and transported out of the weir. On occasion, some porpoise even find their own way out of a weir. Those operating gillnets or weirs should wherever possible attempt to release live porpoise unharmed. Under no circumstances should porpoise be shot. Where necessary advice should be sought from fisheries officers or from researchers associated with the Grand Manan Whale and Seabird Research Station at North Head, Grand Manan.

Coastal chemical contaminants may be responsible for reproductive disorders in small whales, including the Harbour Porpoise. The species is at the top of the coastal food web, has large fat reserves where contaminants concentrate, and as an inshore species is exposed to any contaminants that enter coastal waters. High concentrations of mercury and organochlorine hydrocarbons have been recorded in Bay of Fundy Harbour Porpoise since the 1970s when researchers began to investigate these levels. Monitoring of these contaminants is continuing with some indication that DDT is decreasing, but other chemicals either show no decrease or are increasing.

Many of us, particularly those living in coastal communities, can play a role in keeping coastal marine waters clean. Dispose of toxic wastes responsibly, limit or eliminate pesticide use, and never use the ocean as a garbage dump. Contact the provincial Department of the Environment if you need advice about disposing of waste you believe could be toxic to marine life.