Feel free to use the material on this page for noncommerical purposes only.

Some of the material on this page comes from my Master's thesis:
Torok, M.L. 1994. Movements, Activity Patterns, Dive Behavior, and Food Habits
of Harbor Seals (Phoca vitulina richardsi) in San Francisco Bay, California. 88 pp.

Send any comments or questions to mltorok@volcano.net

Scientific Name (Genus species subspecies): Phoca vitulina richardsi (Pacific Ocean) Phoca vitulina concolor (Atlantic Ocean)	Common Names: Harbor seal, Common seal
Picture: (A picture would be worth a thousand words here, but the fact is I don't have a harbor seal picture handy. As soon as I can get one scanned in, I will put it here.)
All seals belong the the Order Pinnipedia, a word meaning literally "winged foot". Within this Order, harbor seals belong to the Phocid (pronounced fo-sid) Family of seals. Phocid seals do not have any external ears, cannot rotate their hind flippers underneath their body, and move along shore inchworm fashion. In contrast, seals of the Otariid (pronounced o-tar-aye-id) Family such as the California sea lion, have external ears, can rotate their hind flippers underneath their body, and move along shore by "shuffling" their hind and fore flippers. Unlike some of their relatives, harbor seals are not sexually dimorphic. This means there are no significant differences in size between males and females of the same age. Adult harbor seals are approximately 1.3 - 1.6 meters in length and 70 - 100 kilograms in weight. Harbor seals inhabit coastal temperate, subarctic, and arctic waters of the Atlantic and Pacific Oceans, with one of the largest distributions of any pinniped (1). The Pacific harbor seal (Phoca vitulina richardsi) is distributed along the west coast of North America from the Bering Strait to Baja California (1,2). They are non-migratory, with limited seasonal movements of 100 - 300 kilometers associated with breeding, molting, and feeding activities (3,4,5,6). Studies along the west coast of North America in the states of Washington, Oregon, and California have identified estuaries as important areas where harbor seals forage, rest, and rear their pups (5,7,8,9). Harbor seals forage primarily at night and haul-out onshore to rest during the day (10, 11,12,13,14). Excessive disturbance at haul-out sites can alter this pattern. Mean dive duration is directly proportional to seal size, with larger seals averaging longer dives. Adult harbor seal average 3 - 4 minutes per dive, with maximum dive durations of 8 - 10 minutes. Harbor seals are considered opportunistic predators, feeding primarily on abundant benthic (i.e. bottom) and schooling prey. Common prey include fishes (e.g. sculpin, perch, sole, flounder, anchovy, midshipmen, and herring), octopus, squid, and the occassional shrimp (8,15,16). Harbor seals have been implicated in conflicts with commercial fisheries, primarily salmon in the eastern Pacific, and lobster and cod in the western Atlantic. While some direct conflict involving damage to gear and catches has been observed, there is no evidence for significant stock depletion attributed to harbor seals. The timing of birth varies with lattitude, but generally occurs during the months of February to June. Females give birth to a single pup which is weaned in 4 - 6 weeks. Following the weaning period, females reproduce in preparation for the next year's pupping season. The embryo stops developing at a very early stage and implantation in the uterine wall is delayed for several months. About the time of reproduction, harbor seals undergo a yearly moult in which they shed the entire epidermal layer.

References:

1. Bigg, M.A. 1981. Harbor seal, Phoca vitulina Linnaeus, 1758 and Phoca largha Pallas, 1811. pp. 1-27 in Handbook of Marine Mammals, vol. 2: Seals (S.H. Ridgway and R.J. Harrison, eds.). Academic Press, London, 359 pp.

2. Shaughnessy, P.D. and F.H. Fay. 1977. A review of the taxonomy and nomenclature or the northern Pacific harbor seal. J. Zool. (London) 182:385-419.

3. Fancher, L.E. 1979. The Distribution, Population Dynamics, and Behavior of the Harbor Seal (Phoca vitulina richardi) in South San Francisco Bay, California. M.S. Thesis, California State University, Hayward. 109 pp.

4. Sullivan, R.M. 1980. Seasonal occurrence and haul-out use in pinnipeds along Humboldt County, California. J. Mamm. 61(4):754-760.

5. Brown, R.F. and B.R. Mate. 1983. Abundance, movements and feeding habits of harbor seals, Phoca vitulina, at Netarts and Tillamook Bays, Oregon. Oregon Fish Bull. 81:291-301.

6. Allen, S.G., H.R. Huber, C.A. Ribic, and D.G. Ainley. 1989. Population dynamics of harbor seals in the Gulf of the Farallones, California. Calif. Fish and Game 75(4):224-232.

7. Jeffries, S.J. 1986. Seasonal movements and population trends of harbor seals (Phoca vitulina richardsi) in the Columbia River and adjacent waters of Washington and Oregon: 1976-1982. Report to the U.S. Mar. Mamm. Comm., Contract MM2079357-5.

8. Harvey, J.T. 1987. Population Dynamics, Annual Food Consumption, Movements, and Dive Behaviors of Harbor Seals, Phoca vitulina richardsi, in Oregon. Ph.D. Thesis, Oregon State University. 177 pp.

9. Hanson, L.C. 1993. The Foraging Ecology of Harbor Seals, Phoca vitulina, and California Sea Lions, Zalophus californianus, at the Mouth of the Russian River, California. M.A. Thesis, Sonoma State University. 70 pp.

10. Boulva, J. and I.A. McLaren. 1979. Biology of the harbor seal, Phoca vitulina, in eastern Canada. Fish. Res. Board Canada, Bull. 200:1-24.

11. Allen, S.G., D.G. Ainley, and G.W. Page. 1980. Haul out patterns of harbor seals in Bolinas Lagoon, California. Report to the U.S. Marine Mammal Commission, Contract Number MM8AC012.

12. Stewart, B.S. 1984. Diurnal hauling patterns of harbor seals at San Miguel Island, California. J. Wildl. Manage. 48(4):1459-1461.

13. Thompson, P.M. 1987. The Effect of Seasonal Changes in Behavior on the Distribution and Abundance of Common Seals, Phoca vitulina, in Orkney. Ph.D. Thesis, University of Aberdeen. 227 pp.

14. Miller, S.A. (S.G. Allen). 1988. Movement and Activity Patterns of Harbor Seals at Point Reyes Peninsula, California. M.S. Thesis, University of California, Berkeley. 70 pp.

15. Harkonen, T. 1987. Seasonal and regional variations in the feeding habits of the harbour seal, Phoca vitulina, in the Skagerrak and the Kattegat. J. Zool. (London) 213:535-543.

16. Shaffer, K. 1989. Seasonal and Site Variations in the Diets of Harbor Seals, Phoca vitulina richardsi, in Northern California. M.S. Thesis, California State University, Humboldt, California. 66 pp.