A distressed sea lion with a strap embedded in its neck may have been spooked by people who tried to cut it free, the Vancouver Aquarium says.

The marine mammal was spotted on a Cowichan Bay fishing dock with a packing strap cutting into its neck earlier this week.

The Department of Fisheries and Oceans said it would launch a rescue mission with Vancouver Aquarium Marine Mammal Rescue officials this week to tranquilize the animal and cut it free.

But in a Wednesday news release, the rescue centre said the mission may have been hampered by the public.

"We have also been alerted to attempts by members of the public to approach the sea lion and cut the entanglement free with scissors," said spokeswoman Deana Lancaster. "We must emphasize that these rescues should not be attempted by members of the public."

She said despite the best intentions of would-be rescuers, sea lions can get aggressive if they feel threatened.

They can also get spooked and take off, never to return to the same spot – and that's what may have happened in this case.

"Unfortunately, this animal has not been sighted today, which might be a result of being approached," said Lancaster.

That's bad news for an animal with an injury that has been known to kill sea lions in the past.

The rescue centre is asking anyone who spots the sea lion or any other marine mammal in distress to call them at 604-258-7325 or the DFO hotline at 1-800-465-4336.