A rescue team from the Department of Fisheries and Oceans (DFO) and the Vancouver Aquarium were on the water in Cowichan Bay on Thursday, looking for the sea lion seen with a thick plastic band wrapped around its neck.
However, they could not locate the animal.
The sea lion was first seen about a week ago and appeared to be in distress.
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Mary-Ann Miranda Young first saw the sea lion while crab fishing and said it looked like it had been there a long time.
DFO marine mammal co-ordinator Paul Cottrell says the team was notified several days ago and monitored the sea lion to ensure it will stay in the area.
However, it has now gone missing and the rescue team want to warn people not to approach the animal or try to take it upon themselves to remove the rope.
The rescue teams are hoping if the sea lion doesn’t return, someone will see it in another location and they will be able to mobilize there.