Photo courtesy of the Aquarium of the Pacific by Robin Riggs.

On Thursday, Milo the sea lion passed away suddenly, and the aquarium and its visitors are mourning the loss of the playful sea mammal.

Born in 2006 in a fellow Association of Zoos and Aquariums-accredited institution, Milo arrived at the Aquarium of the Pacific in 2007.

“We are deeply saddened by the passing of Milo, and it is a particularly difficult time for staff as he is beloved by so many of us,” Perry Hampton, vice president of animal husbandry at the aquarium, said in a statement. “Milo was loved for his playful nature and big personality, and he will be greatly missed.”

The weekend before Milo died, he showed a loss of appetite, despite having had no pre-existing health conditions, according to the release.

Preliminary treatments, examinations and tests were performed by staff to determine the cause, however Milo passed away suddenly on Thursday afternoon. A necropsy revealed that Milo had died from liver disease, he was 11 years of age.

“Thousands of visitors and staff felt a special bond with Milo, who will be sorely missed,” the aquarium stated.

Milo is survived by his half-brother Harpo, who also arrived at the aquarium in 2007.