Brook, a female otter and one of the Aquarium of the Pacific’s most popular residents, died Tuesday, Jan. 29, officials announced. The facility’s veterinary team diagnosed the animal with congestive heart failure in mid-January.

One of the aquarium’s original charter animals, Brook arrived in 1998 before the aquarium opened to the public. At 21 years of age, she was the oldest female southern sea otter at a zoo or aquarium in the world.

“Brook was known for her photogenic looks and regal demeanor, which landed her image on banners, brochures, and other Aquarium publications and advertisements throughout her life and secured her place in the hearts of the Aquarium’s staff, members, and the public,” stated the release.

In place of the aquarium’s annual Otter Bowl—an otter version of the Puppy Bowl—staff will honor Brook with a tribute video to be posted on social media on Sunday, Feb. 3.

Found stranded at two weeks old in Northern California, Brook was rescued and rehabilitated at a marine mammal center. However, experts decided not to release her back into the wild because she hadn’t learned the survival skills normally taught to sea otter pups by their mothers.

Brook is survived by the aquarium’s other senior otter, Charlie, who at 22, has the distinction of not only being the oldest known otter in the world, but the Guinness Book record holder. Both otters were orphaned in 1997 during El Niño storms.

Male southern sea otters live 10 to 14 years in the wild while females live 12 to 18 years. In a zoo or aquarium environment, they can live up to 20 years or more, according to the aquarium.

Listed as threatened by the Endangered Species Act, sea otters in Southern California were nearly hunted to extinction in the 18th and 19th centuries. In 1938 only 50 remained. While efforts to conserve the population have helped it grow to nearly 3,000, threats remain including habitat loss and ocean pollution.