A sea lion rescued on the west coast of Vancouver Island is in critical condition after staff at the Vancouver Aquarium removed a fish hook and tackle from the animal's gut on Thursday.

People in Ucluelet on the west coast of Vancouver Island spotted the animal in distress on Tuesday and staff at the Aquarium's Marine Mammal Rescue Centre officials rushed to the island on Wednesday to rescue it.

On Thursday veterinarian Martin Haulena removed a fishing hook, a metre of fishing line, and a lure from the sea lion's intestinal tract, along with a large flasher that was hanging from its mouth.

Haulena said it is not yet clear if the 230-kilogram California sea lion, which staff at the Marine Mammal Rescue Centre in Vancouver have named Flash, will survive.

"I am still a little bit worried about what else the hook hit through the esophagus. It was lodged at about the level of the heart.  So perforations there can cause lung problems, thoracic cavity problems, and potentially heart problems as well," said Haulena.

"[He is] certainly not out of the woods yet. He did recover slowly, as was expected due to his poor condition."

Haulena said addition to the internal injuries the sea lion also has an infected wound on its back and around its jaw where it was cut by the fishing line attached to the flasher hanging from its mouth.

"In the best case scenario, he starts to eat on his own, and he starts to heal his esophagus, and heals the jaw and some of his other wounds. He's looking at spending some weeks with us," said Haulena

"In the worst case scenario, there really are a number of things that can go wrong with him," he said.