BODEGA (CBS SF) — Another dead whale has washed up on a Bay Area beach, the seventh so far this year.

The gray whale carcass turned up on Portuguese beach in Sonoma County.

It’s only about 28 feet long—not yet fully grown, and no one knows how it died.

May is the end of the gray whale migration period as they move north from breeding grounds near Mexico.

A dead gray whale that washed onto the shore in Half Moon Bay earlier in the week was spotted Tuesday. Half Moon Bay State Beach Park officials confirmed that that whale washed ashore near Kelly Beach between St. Francis and Poplar.

The gray whale is believed to be nearly 30-feet long.

That was the sixth dead whale to show up on Northern California beaches in the last five weeks. Officials in Pacifica decided to bury the decomposing bodies of two whales that beached there due to complaints over the smell.

On May 4th a whale was found in Pacifica not far from where a dead 48-foot male sperm whale washed ashore on April 14, on Mori Point at the southern end of the beach. Marine Mammal Center officials said they believed it was a coincidence that two whale strandings occurred on the same beach within the same month.

On April 21st, a killer whale also beached itself north of Fort Bragg. Researchers flocked to the Mendocino coast to investigate the rare occurrence. However, they weren’t expected to come to any conclusions as to why the 25-foot creature came ashore to die.

Then on April 24, two gray whale carcasses washed up on a a Santa Cruz County beach.

A 40-foot adult gray whale was found near Waddell Beach. There was no evidence of a ship strike in his death and researchers said it had likely been dead for days.

The second 23-foot yearling found at Pajaro Dunes had killer whale teeth marks on its body and was missing its tongue and jaw. Researchers said its death was likely the result of an orca attack.

A pygmy sperm whale died in January after beaching itself along Point Reyes National Seashore.

The center has responded to 21 humpback whales over the past 40 years, including the famous Humphrey, who became lost in the San Francisco Bay in 1985 and 1990.

There was no word on the cause of the latest whale’s death in Half Moon Bay.

INTERACTIVE MAP OF 2015 WHALE DEATHS:

TM and © Copyright 2015 CBS Radio Inc. and its relevant subsidiaries. CBS RADIO and EYE Logo TM and Copyright 2015 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. Bay City News Service contributed to this report.