Harbor seals

Harbor seals are found throughout the nearshore waters of Washington including Hood Canal, Puget Sound, the San Juan Islands, and the Strait of Juan de Fuca out to Cape Flattery. Harbor seal numbers were severely reduced during the first half of the twentieth century by a state-financed population control program. This bounty program ceased in 1960, and in 1972, harbor seals became protected under the federal Marine Mammal Protection Act (MMPA) and by Washington State. Their populations in Washington State have recovered since the 1970s and population sizes may be near a stable equilibrium level, perhaps reflective of the current carrying capacity of the environment. 

—Source: Puget Sound Science Review

Overview

Harbor seals (Phoca vitulina) are the most commonly seen marine mammals in the Salish Sea and can be found throughout the region year round. They have been intensively studied within the Salish Sea and this species profile provides an overview of what is known about them. It was produced for the Encyclopedia of Puget Sound by the SeaDoc Society. 

Harbor seal vocalizing on rock. Credit: G.E. Davis

Related Articles

Harbor seals were hunted from the 1870s to 1970s until they were protected in the United States by the 1972 Marine Mammal Protection Act and in Canada under the 1970 Marine Mammal Regulations in the Fisheries Act. The inland Washington harbor seal stock is estimated to be over 12,000, while the Strait of Georgia sustains approximately 39,000 harbor seals. Key threats include human disturbance, habitat degradation, loss of prey, and interaction with fishing gear and boats.

Occasionally, our magazine includes reports and essays from guest writers on the subject of Puget Sound ecosystem recovery. Biologist and author Eric Wagner has this look at an ongoing harbor seal survey at the mouth of the Stillaguamish River. Wagner says the study hinges on a basic question: Who is eating the salmon? 

A 2021 paper in the journal PLoS ONE describes a non-traditional approach to estimating the size of three harbor seal management stocks in the inland waters of Washington using aerial line-transect surveys and tagging data.

An article published in the Journal of Wildlife Diseases in 2021 describes trends in birth defects among harbor seals in the Salish Sea from 2003 to 2019. The results suggest a level of congenital disease in this harbor seal population that is important for continued monitoring.

An article published in the Journal of Wildlife Diseases in 2021 describes research documenting injuries among harbor seals in the Salish Sea caused by boat propeller strikes. The number of strikes increased significantly between 2002 and 2019, as did vessel traffic.

Harbor seals and harbor porpoises in the Salish Sea are showing a relatively high presence of antibiotic-resistant bacteria. A 2021 paper in the journal Oceans suggests that these findings may indicate a wider problem among other species in the region.