A member of the public took to Facebook, sharing an image and a video of the sea lion.
Doc’s biodiversity supervisor Jim Watts said they were working alongside the New Zealand Sea Lion Trust to help "form a response plan".
"Doc was notified over the weekend of a sea lion that appears to have a fishing line around its neck and mouth," he said.
A Doc ranger headed out to the sea lion’s last known location to gain more information.
Mr Watts encouraged the public, if they saw the sea lion, to give it space and report it to 0800DOCHOT.
"As sea lions are highly mobile, any response will require a team of experts to be ready to respond at short notice, so up-to-date sightings from the public are important."
He hoped to remind people to report injured wildlife to the hotline "as soon as they can".
"We would rather be notified several times over the same incident than not at all."
The sea lion was found within the Ōrau marine reserve — one of six marine reserves across the region.
Marine reserves were approved in October but were yet to come into force. The decision was made to help protect marine life and their habitats.
Recently, the Otago Rock Lobster Industry Association filed a judicial review in the Wellington High Court to fight the establishment of the region’s marine reserves.
