SEATTLE — A count of orcas in the Pacific Northwest indicates that no calves have been born for the last three years, resulting in a 30-year population low.

The Seattle Post-Intelligencer reports the annual census of Puget Sound's killer whales has counted 75 across three Southern Resident pods.

The census also reported two orcas missing and presumed dead.

Researchers say the dwindling whale numbers are linked to pollution and a decreasing primary food source.

Pollution can accumulate in the orca's prey and get stored in their fat, making the killer whales more susceptible to disease by a suppressed immune system. The main food source for Orcas is Chinook salmon, which are not as numerous as they once were.

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