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Doc was alerted to the entangled penguin by a member of the public, who called the Doc hotline.
The bird was freed and unharmed.
Hokitika operations manager Nicole Kunzmann said rubbish and marine debris was an increasing problem for wildlife.
"Seabirds and marine mammals become entangled in or ingest rubbish, often leading to injury or death. This penguin had a lucky escape because it was found.
Others won't be so fortunate.
"If you see fishing line or other plastic rubbish on our West Coast beaches, please help by picking it up and removing it. If you see a bird or marine mammal that is entangled in plastic rubbish, call the Doc hotline 0800 362 468."
The little blue penguin is the world's smallest penguin, with an estimated 800 to 1000 on the West Coast.
They can be seen after dusk and just before dawn walking across the beach, between nests and the sea.