An endangered green sea turtle died early Monday at the Vancouver Aquarium after being rescued four nights earlier on Vancouver Island.

The tropical turtle was found Wednesday and is the second in a week to wash up on the shores of the Pacific Rim National Park Reserve near Tofino. Scientists are baffled as to why.

Dr. Dennis Thoney, director of animal operations at the aquarium, said it is unknown where the turtles came from exactly and how they ended up in cold B.C. waters during a La Nina year.

"Normally when we see turtles up here it's during times of El Nino when the waters are much warmer and they tend to move further north. But this year, it's the opposite," he said.

On Wednesday, a park visitor spotted the sick turtle stranded on the beach and immediately notified Fisheries and Oceans Canada's Marine Mammal Response Network, which rushed to the scene and transferred the reptile to Vancouver.

Aquarium veterinarian Dr. Martin Haulena and his team provided emergency treatment to the young male sea turtle including feeding him fluids and antibiotics.

The cold-shocked animal also had severe eye injuries that seemed to be improving with rehydration. However, the turtle's lack of response and slow movements led veterinarians to believe he may have been brain dead.

Last week, an olive ridley sea turtle was found in the same region but was declared dead the day after it was brought to the aquarium.

Aquarium veterinarians were hoping for a better outcome for the second young sea turtle but with such a slow heart rate, they were skeptical of his recovery.

"Reptiles have a capability of slowing down to hibernate over winter and then come out," Thoney said. "But they're tropical animals so it's not a normal thing. It could kill him."

The Vancouver Aquarium urges the public to report dead, injured and distressed marine mammals and sea turtles to the Marine Mammal Response Network hotline at 1-800-465-4336.

Any sightings of live, free-swimming sea turtles and cetaceans should be reported to the Vancouver Aquarium's BC Cetacean Sightings Network at 1-866-ISAWONE.