Mystic — Kodiak, a 15-year-old male Steller sea lion that was a favorite with visitors to Mystic Aquarium, died Friday after efforts to save him from liver disease and kidney failure were unsuccessful, the aquarium said in a press release.

The aquarium said the 2,000-pound Kodiak came to Mystic Aquarium from Vancouver Aquarium in 2002.

“Mystic Aquarium trainers were continually impressed by his intelligence and ability to learn new behaviors,” the release said.

The Steller sea lion is the largest member of the eared seal family and is found mainly around Northern Pacific coasts, the release said. Divided into eastern and western regions, the western population is endangered and the eastern population is threatened.

The release said the sea lion had to be humanely euthanized despite “extraordinary efforts” by the aquarium’s animal care team and marine mammal specialists nationwide.

A necropsy will be performed, the release said.