The Department of Conservation is urging the public to come forward with information after a critically endangered sea lion/rāpoka was shot on a South Otago beach.

Biodiversity ranger Ros Cole says the male sea lion was reported dead on Tautuku Beach southwest of Balclutha on Sunday.

"A local vet performed a necropsy confirming what we suspected - the sea lion had been shot," she said.

"It's really disheartening someone would do this, sea lions are not only critically endangered but also a taonga species special to Ngāi Tahu. To discover someone has such reckless disregard for our protected species is extremely disappointing."

The sea lion appeared to be otherwise healthy and in good condition, she said.

Sea lions are fully protected in New Zealand, with the same threat classification as kākāpō and kiwi.

In July, the Sea Lion Threat Management Plan was released which aims to halt the decline of the sea lion population within five years and ensure the population is stable or increasing within 20 years.

A particular goal for the South Island is that there are no cases of deliberate human-caused mortality for sea lions.

It is illegal to injure or kill sea lions and anyone apprehended faces serious penalties, including up to two years' imprisonment and a fine of up to $250,000 under the Marine Mammals Protection Act 1978 and five years' prison and a fine of up to $100,000 under the Animal Welfare Act 1999.

This is the second time a sea lion had been shot on the Catlins coast this year. In April another male was found dead at Jacks Bay.

Anyone with any information on the shot sea lion is urged to contact the Owaka Police on 03 419 1070.