Trends and Status of Harbor Seals in Washington State: 1978-99

In the first half of the twentieth century, the number of harbor seals (Phoca vitulina richardsi) in Washington State was severely reduced by a state-financed population control program, which considered harbor seals to be predators in direct competition with commercial and sport fishermen. Seals began to recover after the bounty program ended in 1960 and the Marine Mammal Protection Act was passed in 1972.

From 1978 to 1999, biologists from the Washington Department of Fish and Wildlife (WDFW) and National Marine Mammal Laboratory (NMML) flew aerial surveys to determine the distribution and abundance of harbor seals in Washington. We used exponential and generalized logistic models to examine population trends and status relative to maximum net productivity level (MNPL) and carrying capacity (K). Since 1978, harbor seal counts have increased threefold, and estimated abundance has increased seven- to tenfold since 1970.

This study highlights the importance of long-term precise monitoring to help understand population dynamics and support management decisions. The report is based on the article "Trends and Status of harbor seals in Washington State: 1978-1999" by S.J. Jeffries, H. R. Huber, J. Calambokidis, and J.L. Laake appearing in the Journal of Wildlife Management, January 2003. The study was initiated by S.J. Jeffries at WDFW in 1975.

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AFSC Quarterly
Research Reports
Oct.-Dec. 2002