A sea lion found with a gunshot wound to his head off the west coast of Vancouver Island has been taken to a rescue centre for treatment.

The adult male Steller sea lion was found unresponsive but still alive on a rocky shoreline of Ucluelet last Thursday, according to the Vancouver Aquarium Marine Mammal Rescue Centre.

He had been lying there for more than a day and it took a massive team of personnel to rescue him, including crews from the rescue centre , the Department of Fisheries and Oceans, Parks Canada, local volunteers and a truck and crane from Windsor Plywood.

While the massive sea lion dubbed "Ukee" is the largest-ever animal admitted to the rescue centre, he is still considered severely emaciated by veterinarians.

Preliminary exams also showed at least one bullet lodged in the sea lion's skull, and experts say he may also be blind and unable to forage for food. He is estimated to be between 8-10 years old and weighing between 300 and 350 kilograms, far below the 800 kilograms that some adult Steller sea lions can weigh.

"He’s very skinny, very lethargic," said aquarium veterinary fellow Dr. Megan Strobel. "Over the weekend, we treated him with supportive therapy, fluids and medication. This week, we’ll do x-rays and ultrasounds and get a better idea about the extent of his injuries."

Ukee's condition remains critical and he won't eat fish offered to him.

Aquarium teams were nonetheless encouraged when the sea lion took a dip in his pool over the weekend.

He's the second sea lion within a year-and-a-half to be admitted to the rescue centre with gunshot sounds. An adult male California sea lion was rescued from Spanish Banks in Vancouver in May 2017 and determined to have been shot in the head, breaking some of his teeth. The animal was later deemed non-releasable by Fisheries and Oceans Canada and is now living at the Vancouver Aquarium.

As for Ukee, rescuers are thanking those who called in to report his condition – and have stern words for whoever shot him.

"This is clearly a serious animal welfare issue," said Dr. Martin Haulena, head veterinarian at Vancouver Aquarium. "It is unacceptable to shoot sea lions. Based on his body condition, this individual has been suffering for many weeks."

Anyone who sees a marine mammal in distress is asked to stay back, keep people and pets away, and report it to the rescue centre at 604-258-7325 or the DFO hotline at 1-800-465-4336.