The harbor seal is a carnivore and feeds on a variety of fish, octopus, squid, shrimp, crabs and mollusks and seabirds, all depending on the prey native to its environment. Although carnivorous and quite large, Harbor seals pose no threat to humans. While very capable swimmers, when hauled-out on land Harbor seals are very vulnerable and will often rush back into the water if approached.
Once heavily hunted by people, the harbor seal is a protected animal in almost every nation now and its population is on the rebound. However, urbanization of coastal areas remains a threat to these animals. In order to rest and molt, harbor seals need to spend a lot of time out of the water, and if a human presence is detected they will often not haul out. If construction occurs at or near a usual haul-out spot, the seals will sometimes abandon it permanently, which could threaten their population.