A total of 21 gray whale deaths have been recorded this year in the San Francisco Bay Area — the highest count in 25 years, according to the Marine Mammal Center.

The most recent case occurred on July 7, when a whale believed to have been struck by a vessel washed ashore in Richmond, the Sausalito-based center and the California Academy of Sciences reported Thursday.

Scientists say this is the largest number of gray whale deaths in the region since 2000 and reflects ongoing population challenges for the species.

The National Oceanic and Atmospheric Administration (NOAA) recently updated its population estimate, revealing that the number of eastern North Pacific gray whales has dropped to approximately 13,000 — the lowest since the 1970s.

The Richmond whale, a young female in otherwise good physical condition, was discovered floating beneath the Richmond Long Wharf near the Richmond-San Rafael Bridge.

Researchers transported the carcass to Angel Island State Park on Thursday for a necropsy to determine the exact cause of death.