Last modified: Thursday September 24th, 1999

Harbor porpoise

Phocoena phocoena (Linneaus, 1758)

Taxonomy

The harbor porpoise is generally considered to be a single species. Some have suggested three subspecies: Phocoena phocoena relicta in the Azov and Black Seas, Phocoena phocoena phocoena in the North Atlantic and Phocoena phocoena vomerina in the North Pacific (Klinowksa, 1991). However, this subdivision is not widely accepted.

Appearance

The harbor porpoise is a small, stocky animal.The dorsal side is brown or dark grey, converging to a lighter grey on the flanks. The triangular dorsal fin is located in the middle of the back (Minasian et al, 1984). The average length is 1.5 m. with a maximum size of about 2 m. Females are slightly larger than males. They weigh 45-65 kg, with a maximum of 90 kg (Evans, 1987; Peet et al., 1992).

Distribution

The harbor porpoise is a coastal species, limited to the cold temperate and subarctic waters of the Northern Hemisphere. In the Eastern North Atlantic it ranges from the Kara Sea south to Senegal, Africa, including the North Sea, the Baltic Sea and the Western Mediterranean. There is an isolated population in the Black Sea. In the Western North Atlantic, this species ranges from southern Greenland to North Carolina, USA. and there is also a population around Iceland. In the Eastern Pacific, it ranges from Alaska (up to Point Barrow) south to California. In the Western Pacific, the species ranges from the Bering Sea to northern Japan (Klinowksa, 1991). There is no clear migration. Most of the travelling seems to be related to movement of food resources.

Population dynamics and life history

The maximum age for harbor porpoises is about 17 years. The mean age at sexual maturity for females is 3.1 to 3.4 years. Pregnancy lasts about 10.6 months, followed by 8 to 12 months of lactation (Palka et al, 1996).

Population status

The harbor porpoise population in the North Sea has declined considerably since the second World War (Verwey, 1975), but seems to have recovered slightly (Reijnders et al, 1996).

Harbor porpoise abundance estimates
Region Abundance
Gulf of Maine - Bay of Fundy 47,200
Iceland 27,000
North Norway, Barents Sea 11,000
Kattegat, Skagerrak and Bælt areas 36,000
Baltic Sea unknown, low
North Sea 279,300
Ireland and Western UK 32,280

Feeding

The diet of the harbor porpoise is varied and differs geographically and seasonally. Common prey species include herring, hake, lantern fish, capelin as well as cephalopods (Palka et al, 1996). Also anchovy and loligo are taken (Sekiguchi, 1995). Total food intake is between 4 and 9.5% of the total body weight, representing between 8000 and 25000 kJ/day (Kastelein, Hardeman and Boer, 1997). Harbor porpoises have been observed swimming into schools of fish. When large schools of fish are available, the porpoises seem to concentrate around them (Baptist and Witte, 1996).

Exploitation and threats

In the past, the harbor porpoise has been hunted throughout its range for food and oil. There has been a major fishery for this species in the Lille Bælt in Denmark from the 1830s until the second World War, in which several hundred to more than thousand animals were taken annually. There has also been a drive fishery in the Black Sea. Before the second World War, this fishery took 100,000-300,000 animals per year, which declined to 5,000-7,000 per year in the mid-1960s. This fishery targeted harbor porpoises, common dolphins and bottlenose dolphins. The composition of the catch is unknown. The Turkish fisheries, which was suspended in 1983, took 34,000-44,000 animals per year between 1976 and 1981. Harbor porpoises made up about 80% of the total catch (Klinowksa, 1991)

Currently, the main threat for the harbor porpoise is the high level of bycatch. The International Whaling Commission (1996) reports the following bycatch estimates for the North Atlantic:

Harbor porpoise annual bycatches
Region Bycatch
Gulf of Maine - Bay of Fundy 1,000-4,000
Greenland > 700
Kattegat, Skagerrak and Bælt areas > 250
Baltic Sea ~ 10
North Sea 4,000-5,000
Ireland and Western UK 2,000

The IWC concluded that the current bycatch in the North Sea may not be sustainable. In the area where most of the bycatch occurs, 3.1% of the population is killed this way annually. Recently, the Agreement on the Conservation of Small Cetaceans of the Baltic and North Seas (ASCOBANS) was set up to provide an international platform for the conservation of among others the harbor porpoise. A number of countries already signed and ratified this agreement.

Also, most of the common prey species of the harbor porpoise (herring, mackerel, sprat, pilchard, whiting, cod) are also commercially exploited species. In addition to the threats of entanglement, this also means that depletion of food resource by fisheries is a risk (Hutchinson, 1996).

Rehabilitation

In areas where the harbor porpoise is relatively abundant, strandings of sick and injured animals are not uncommon. Animals stranding on the Western European coastline are usually transfered to the rehabilitation center at the Dolfinarium in Harderwijk, the Netherlands. The park has a dedicated rehabilitation center for small cetaceans since 1991. See Kastelein, Bakker and Staal (1997) for details on the rehabilitation process.

References

Baptist, H. and R. Witte (1996).
Opmerkelijke foerageer-methode van bruinvissen.
Zoogdier 7(3): 9-11.
Evans, P.G.H. (1987)
The natural history of whales and dolphins. Christopher Helm, London.
Hutchinson, J. D. (1996).
Fisheries interaction: the harbour porpoise - a review.
in: M. P. Simmonds and J. D. Hutchinson. : The conservation of whales and dolphins - Science and practice, pp. 129-165. John Wiley & Sons, Chichester
ISBN: 0-471-96561-8.
International Whaling Commission (1996)
Report of the sub-committee on small cetaceans. Rep. Int. Whal. Commn. 46:160-179
Kastelein, R.A., M.J. Bakker and C. Staal (1997)
The rehabilitation and release of stranded harbour porpoises (Phocoena phocoena).
in: A.J. Read, P.R. Wiepkema and P.E. Nachtigall: The biology of the harbour porpoise, pp. 9-61. De Spil B.V. Publishers, Woerden the Netherlands
ISBN: 90-72743-07-5.
Kastelein, R.A, J. Hardeman and H. Boer (1997).
Food consumption and body weight of harbour porpoises (Phocoena phocoena).
in: A.J. Read, P.R. Wiepkema and P.E. Nachtigall: The biology of the harbour porpoise, pp. 217-233. De Spil B.V. Publishers, Woerden the Netherlands
ISBN: 90-72743-07-5.
Klinowska, M. (1991)
Dolphins, Porpoises and Whales of the World. The IUCN Red Data Book. IUCN, Gland, Switzerland.
Minasian, S.M., Balcomb III, K.C. and Foster, L. (1984)
The world's whales. The complete illustrated guide. Smithsonian Books, Washington D.C.
Palka, D. L., A. J. Read, A. J. Westgate and D. W. Johnston (1996).
Summary of current knowledge of harbour porpoises in US and Canadian Atlantic waters.
in: Forty-Sixth Report of the International Whaling Commission, pp. 559-565 (SC/47/SM23). International Whaling Commission, Cambridge
ISBN: 0 906975 35 2.
Peet, G., H. Nijkamp, P.-H. Nelissen and F.-J. Maas (1992).
Bruinvissen, dolfijnen en walvissen van de Noordzee . M & P Uitgeverij b.v., Weert
ISBN: 90 6590 614 2.
Reijnders, P. J. H., M. F. Leopold, C. J. Camphuysen, H. J. L. Heessen and R. A. Kastelein (1996).
The status of the harbour porpoise, Phocoena phocoena, in Dutch waters and the state of related research in the Netherlands: an overview.
in: Forty-Sixth Report of the International Whaling Commission, pp. 607-611 (SC/47/SM41). International Whaling Commission, Cambridge
ISBN: 0 906975 35 2.
Sekiguchi, K. (1995).
Occurrence, behavior and feeding habits of harbor porpoises (Phocoena phocoena) at Pajaro Dunes, Monterey Bay, California.
Aquatic Mammals 21(2): 91-103.
Verwey, J. (1975)
The cetaceans Phocoena phocoena and Tursiops truncatus in the Marsdiep Area (Dutch Waddensea) in the years 1931-1973.
Internal report 17, Netherlands Institute for Sea Research


About the pictures

The pictures on this page were taken at the Fjord- og Bælt Centret in Kerteminde, Denmark. At this aquarium, two harbor porpoises (incidentally caught animals) are kept for research purposes. The research is aimed at reducing bycatches.


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