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 seal species profile
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.
RELATED ARTICLES

Interannual differences in postrelease movements of rehabilitated harbor seal pups (Phoca vitulina richardii) in the Salish Sea
A study published in Marine Mammal Science in June 2020 followed the movements and behavior of rehabilitated harbor seal pups after being released into the Salish Sea. The results suggest that although their movements differ from wild pups that have been weaned, the rehabilitated pups do successfully make the transition.

History of food web found in harbor seal skulls
Tiny bone samples show that seals alter their diets as conditions change. The findings could help scientists understand whether seals are contributing to local salmon declines.

Probing for answers to control seal populations
Last month's federal authorization to kill more than 700 sea lions to protect salmon runs along the Columbia River is prompting discussions of similar actions for harbor seals in Puget Sound. But experts say the situations are very different with many unanswered questions.

Fungal disease a rising concern for local marine mammals
A 2020 paper published in Frontiers in Marine Science describes details of the fungal disease Mucormycosis which has caused the death of harbor porpoises, harbor seals and one orca in Puget Sound in recent years. The authors discuss the implications for local marine mammals, specifically the endangered southern resident killer whale population.

Causes of mortality in a harbor seal (Phoca vitulina) population at equilibrium
A 2020 article in the journal Frontiers in Marine Science looks at harbor seal stranding and necropsy findings in the San Juan Islands to assess age-related stranding trends and causes of mortality. The harbor seal (Phoca vitulina richardii) population in the Salish Sea has been at equilibrium since the mid-1990s. This stable population of marine mammals resides relatively close to shore near a large human population and offers a novel opportunity to evaluate whether disease acts in a density-dependent manner to limit population growth.

The occurrence of heavy metals in harbor seals of the San Juan Islands
A 2019 article in the Journal of Wildlife Diseases looked at trace element concentrations of heavy metals in the livers of harbor seals that died and stranded in the San Juan Islands. The study indicated exposure to trace elements (naturally occurring, human-introduced, or both) in the Salish Sea; however, the study reports that trace element toxicity is not a major threat to harbor seal health.

Fine-scale variability in harbor seal foraging behavior
A 2014 paper in the journal PLoS ONE examines differences between foraging behavior of harbor seals based on haulout site locations, seasons, sexes and times of day. The authors hypothesize that these factors may help explain the variability in diet among harbor seals observed at different haul-out site groups in the Salish Sea.

Study would explore changes to protections for seals and sea lions
As wildlife managers work to recover Puget Sound’s diminished Chinook population, a proposed white paper is expected to review the impacts of some of the salmon's chief predators. The study would include a section on potential management of seals and sea lions, prompting open discussion of a long taboo subject: Could officials seek to revise the Marine Mammal Protection Act — or even conduct lethal or non-lethal removal of seals and sea lions in some cases? Such actions are hypothetical, but we look at some of the ongoing discussions around the issue as prompted by a new resolution from the Puget Sound Leadership Council.

Influence of human exposure on the anti-predator response of harbor seals (Phoca vitulina)
A 2017 paper in the journal Aquatic Mammals reports that harbor seals in the Salish Sea are less concerned about predators when they become habituated to humans.

Seals and sea lions may be slowing salmon recovery, hurting orcas
Increased consumption of Chinook salmon by seals and sea lions in the Salish Sea “could be masking the success of coastwide salmon recovery efforts,” according to a new study published in the journal Scientific Reports. Endangered resident orcas are said to be declining in part due to a lack of available Chinook, the orcas' preferred prey.

Harbor seal (Phoca vitulina) tolerance to vessels under different levels of boat traffic
Vessel traffic is increasing in the Puget Sound region. A 2017 article in the journal Aquatic Mammals looks at the potential impacts that increasing vessel disturbance may have on resident harbor seal populations and how future management decisions may need to look at variable buffer zones related to level of human activity.

Study says predators may play major role in chinook salmon declines
A new study shows that increased populations of seals and sea lions are eating far more of Puget Sound’s threatened chinook than previously known, potentially hampering recovery efforts for both salmon and endangered killer whales.

Advances in technology help researchers evaluate threatened Puget Sound steelhead
New, smaller acoustic tags will allow scientists to track steelhead migrations in Puget Sound in ways that were once impossible. Will they provide answers to the mysterious decline of these now-threatened fish?
Conjoined fetal twins in a harbor seal (Phoca vitulina)
This article describes the first known case of conjoined twins in a harbor seal. The case was documented in the Salish Sea region where harbor seals are often used as indicators of contaminant levels. However, researchers say their findings do not support that this anomaly was due to any common contaminants and hypothesize that the twinning was caused by disordered embryo migration and fusion.

Foraging differences between male and female harbor seals present challenges for fisheries management
A 2015 article published in the Marine Ecology Progress Series identifies intraspecific differences in diet between harbor seals in the Salish Sea, suggesting implications for marine reserve management.

What is killing young salmon in Puget Sound?
Scientists say Puget Sound’s salmon are dying young and point to low growth rates in the marine environment as a possible cause. In part one of this two-part series, scientists consider threats facing young salmon in the open waters of Puget Sound.

Age, region, and temporal patterns of trace elements measured in stranded harbor seals (Phoca vitulina richardii) from Washington inland waters
A 2014 article in the journal Northwestern Naturalist shows how Harbor Seal tissues can reflect regional and temporal trends in contaminants in Puget Sound.

Paper: Food habits of harbor seals (Phoca vitulina) in two estuaries in the central Salish Sea
This paper discusses the dietary habits of harbor seals (Phoca vitulina) in two estuaries in Puget Sound.

Brucella pinnipedalis infections in Pacific harbor seals in Washington State
This paper discusses Brucella pinnipedalis infections in harbor seals (Phoca vitulina) in Washington state and transmission to humans and other wildlife. The disease poses a threat to endangered populations and may be exacerbated by organic pollutants.

Influence of sex and body mass on harbor seal (Phoca vitulina) diving behavior
A master's thesis prepared at Western Washington University discusses the impact of harbor seals on fish stocks in the San Juan Islands, where the seals are a year-round predator.

Harbor seals
Harbor seal numbers were severely reduced in Puget Sound 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 and by Washington State.