posted August 16, 2011 10:49 PM            

An adult female gray whale that lived in Northern California's Klamath River for 53 days died early Tuesday after beaching itself twice on a sandbar.

The 45-foot cetacean, which had become beloved by locals and tourists, developed respiration problems Monday afternoon and had trouble swimming in an upright position. On Monday evening it beached itself on a sand bar in the middle of the river. It was coaxed back into the river, but swam back onto the sandbar. The whale perished at about 4 a.m.

Photographer Ashala Tylor, who has chronicled the whale's time in the river on her blog, posted this entry Monday night: "Please send love and light or prayers,or just plain good energy, to our beautiful whale, Mama. Tonight she floated down the river towards the ocean and is now caught on a sandbar [at] low tide.

"...Please send good energy and prayers that this wonderful being will either pass on easily or somehow make it out to the ocean. She has graced our river with nothing short of love and dignity and brought thousands of people together to share in her magnificence

Scientists on Tuesday were conducting a necropsy in the hope of pinpointing a precise cause of death.

"Based on the photos and everything, her fat layer looks good, so we don't think she starved to death. There's something else going on," Sarah Wilkin, stranding coordinator for NOAA Fisheries, told the Associated Press.

The mother whale entered the river on June 23 with her calf, during the species' migration from Baja California nursing grounds to Arctic home waters. They immediately became a tourist attraction.

After the calf swam back into the ocean on July 23, facing an uncertain future, marine mammal experts and members of the Yurok Tribe, whose reservation lines the banks of the river, tried many tactics in an attempt to persuade the 40-ton female whale to leave.

They included blasting water cannons, banging on pipes, chanting and broadcasting killer whale sounds. Tourists serenaded the whale with music and song. Some even prayed while in the company of the whale, hoping "Mama" would leave for her own good.

Thomas O'Rourke, chairman of the Yurok Tribe, told the AP: "It's very sad. It started to become a part of the community."

-- Top photo: Yurok Fisheries staff examine the deceased whale located just below the Highway 101 bridge on the Klamath River. The Yurok Tribe, NOAA Fisheries and Humboldt State University are working on plan to remove the whale from the waterway. Credit: Matt Mais / Yurok Tribe