Habit:Coastal

Some harbor porpoise populations migrate, such as those on the eastern coasts of the U.S. and Canada. Other populations have more restricted movements, as do stocks on the western coast of the continental U.S. Geographic ranges of distinct stocks are often finely scaled.

Most harbor porpoise groups are small, generally consisting of less than five or six individuals. They do, at times, aggregate into large, loose groups of 50 to several hundred animals, mostly for feeding or migration. Behavior tends to be inconspicuous, compared to most dolphins. Harbor porpoises rarely approach boats to ride bow waves, and often actively avoid vessels. When moving slowly they tend to surface in a slow gentle roll. When moving fast, they surface in a behavior often called pop-splashing. Breaches and other leaps are rarely seen. Harbor porpoises sometimes lie at the surface for brief periods between submergences, although it is not known why they do this.

Reproductive biology has been well-studied in some parts of the world. Sexual maturity is generally reached at 3-4 years of age, with geographic and density-dependent variation. In some areas of this species’ range females give birth every year, while in others harbor porpoises give birth every other year. Pregnancy lasts 10.6 months, most calves being born from spring through midsummer. Lactation is thought to last between 8 and 12 months. Females in some stocks are likely to be pregnant and lactating simultaneously, placing heavy energy requirements on these individuals. This is a relatively short-lived odontocete, in which specimens living past 20 years are rarely found.

Broad diet dominated by:Fish > squid > invertebrates

Harbor porpoises eat a wide variety of fish and cephalopods, and the main prey items appear to vary regionally. Small, non-spiny schooling fish (such as herring and mackerel) are the most common prey in many areas, and many prey species are benthic or demersal.

Feeding mode:Seizing

Known prey items:

Fish:Mallotus villosus, Clupea harengus, Sebastes marinus, Scomber scombrus, Gadus morhua, Ammodytes sp., Pleuronectidae, Salmonidae, Osmerus mordax, Merluccius bilinearis, Pollachius virens, Macrozoarces americanus, Myxine glutinosa, Urophysis sp., Sprattus sprattus, Melanogrammus aeglefinus, Pollachius pollachius, Merlangius merlangius, Micromesistius poutassou, Trisopterus esmarkii, Trisopterus minutus, Enchelyopus cimbrius, Gobidae, Anguilla anguilla, Maurolicus muelleri, Merluccius merluccius, Spondyliosoma cantharus, Lycodes vahlii, Maurolicus weitzmani, Peprilus triacanthus, Alosa pseudoharengus, Pleuronectes americanus

Cephalopods:Loligo pealei, Bathypolypus arcticus, Loligo subulata, Loligo vulgaris, Rossia macrosoma, Sepietta oweniana, Illex illecebrosus

Nereis sp., Meganyctiphanes norvegica, Pandalus montagui

Main threats:

Fisheries bycatch

Entanglement in fishing gear

Harvest

Organochlorine contamination

Conservation status:

The IUCN classifies harbor porpoises as a vulnerable species, although the U.S. government does not consider the species threatened or endangered in its waters. The harbor porpoise faces many threats at the hands of humans. The species has been hunted in many areas of its range, and the major kills once occurred in the Bay of Fundy, Danish Baltic Sea, Black Sea, and Greenland. Today, the most significant threat in most areas is incidental catches in fishing nets, primarily various types of gillnets. Kills of over 1,000 porpoises per year have been documented for the Gulf of Maine, West Greenland, North Sea, and Celtic Shelf, but smaller kills occur in many other areas. In addition to gillnets, harbor porpoises are also taken in trawls, Japanese set nets, herring weirs, pound nets, and cod traps. Finally, other types of threats include pollution, vessel traffic, noise, and overfishing. Environmental contaminants may also pose a threat in some heavily industrialized areas.

The National Marine Fisheries Service considers animals in U.S. waters to be members of several distinct stocks, and assesses them separately. Delineations between stocks are often difficult to determine, therefore assessments should be considered ongoing processes. Stocks are estimated as follows

Morro Bay stock – 932 (CV=0.41) based on 1997-1999 aerial surveys

Monterey Bay stock – 1,603 (CV=0.42) based on 1997-1999 aerial survey data

San Francisco-Russian River stock – 6,674 (CV=0.39) based on 1997-1999 aerial survey data

Northern California/southern Oregon stock – 17,763 (CV=0.39) based on 1997-1999 aerial survey data

Oregon/Washington coast stock – 39,586 (CV=0.384) based on 1997 aerial survey data

Washington Inland Waters stock – 3,509 (CV=0.396) 1997 estimate based on aerial surveys conducted in 1996

Southeast Alaska stock – 10,508 (CV=0.274) based 1997 aerial survey data

The Gulf of Alaska stock -- 21,451 (CV=0.309) based on 1998 aerial survey data

Bering Sea Stock – 10,946 (CV=0.300) based on 1991 aerial survey

Gulf of Maine/Bay of Fundy stock (inhabiting both U.S. and Canadian waters) -- 89,700 (CV=0.22) based on 1999 survey data.

For further information regarding the methods used to estimate abundance, consult the most current assessment report for each stock.

For current information on the conservation status of this species, please consult the following websites.

CITES web-page

Convention on Migratory Species (Appendix II North and Baltic Sea population, western Atlantic population, and Black Sea population)

International Whaling Commission

U.S. NMFS Stock Assessment Reports

Genetics Genbank

Images Google Images

Museum Collections Smithsonian Institution

Bjorge, A. and K.A. Tolley. 2002. Harbor porpoise Phocoena phocoena. Pp. 549-551 in W.F. Perrin, B. Würsig and J.G.M. Thewissen, eds. Encyclopedia of marine mammals. Academic Press.

Boerjesson, P., P. Berggren, and B. Ganning. 2003. Diet of harbor porpoises in the Kattegat and Skagerrak seas accounting for individual variation and sample size. Marine Mammal Science 1938-58.

Fontaine, P.M., M.O. Hammill, C. Barrette, and M.C. Kingsley. 1994. Summer diet of the harbour porpoise (Phocoena phocoena) in the estuary and northern Gulf of St. Lawrence. Canadian Journal of Fisheries and Aquatic Sciences 51172-178.

Gannon, D.P., J.E. Craddock, and A.J. Read. 1998. Autumn food habits of harbor porpoises, Phocoena phocoena, in the Gulf of Maine. Fishery Bulletin 96428-437.

Gaskin, D.E. 1992. Status of the harbour porpoise, Phocoena phocoena, in Canada. Canadian Field-Naturalist 106:36-54.

Gonzalez, A.F., A. Lopez, A. Guerra, and A. Barreiro. 1994. Diets of marine mammals stranded on the northwestern Spanish Atlantic coast with special reference to Cephalopoda. Fisheries Research 21179-191.

Koschinski, S. 2002. Current knowledge on harbour porpoises (Phocoena phocoena) in the Baltic Sea. Ophelia 55:167-197.

Nachtigall, P.E., J. Lien, W.W.L. Au, and A.J. Read. 1995. Harbour porpoises Laboratory studies to reduce bycatch. De Spil Publishers, 167 pp.

Read, A.J. 1999. Harbour porpoise Phocoena phocoena (Linneaus, 1758). Pp. 323-356 in S.H. Ridgway and R. Harrison, eds. Handbook of marine mammals, Vol. 6 The second book of dolphins and the porpoises. Academic Press.

Read, A.J. and A.A. Hohn. 1995. Life in the fast lane the life history of harbor porpoises from the Gulf of Maine. Marine Mammal Science 11423-440.

Read, A.J., P.R. Wiepkema, and P.E. Nachtigall. 1997. The biology of the harbour porpoise. De Spil Publishers, 409 pp.

Recchia, C.A. and A.J. Read. 1989. Stomach contents of harbour porpoises, Phocoena phocoena (L.), from the Bay of Fundy. Canadian Journal of Zoology 672140-2146.

Rosel, P. 1997. A review and assessment of the status of the harbor porpoise (Phocoena phocoena) in the North Atlantic. Pp. 209-226 in A.E. Dizon, S.J. Chivers and W.F. Perrin, eds. Molecular genetics of marine mammals. The Society of Marine Mammalogy.

Smith, G.J.D. and D.E. Gaskin. 1974. The diet of harbour porpoises (Phocoena phocoena (L.)) in coastal waters of Eastern Canada, with special reference to the Bay of Fundy. Canadian Journal of Zoology 52777-782.