A decapitated dolphin has been found on a beach north of Kaikōura.

A member of the public reported the discovery to the Department of Conservation (DOC) on 24 August.

DOC said it appeared to be a dusky dolphin that had washed up naturally before someone illegally removed its head.

Kaikōura Marine Reserves Ranger Zac Penman said the "grisly act" was a breach of the Marine Mammals Protection Act.

"It's not acceptable for people to interfere with protected wildlife and it's illegal to remove a protected species' head," he said.

Penman said Kaikōura was renowned for its marine life and wildlife-watching opportunities.

"Countless dolphins, seals, whales and other marine animals count on us to do our part and follow the rules," he said.

"When people or organisations don't follow the rules, it threatens our special places and native wildlife. DOC takes these responsibilities very seriously and has a range of enforcement tools to hold rule-breakers to account."

In June, DOC reported the discovery of two headless kekeno/fur seals on Muriwai Beach in Auckland.

DOC urged anyone with information on the decapitated dolphin to call 0800 DOC HOT or email [email protected] with the reference number CLE-9721.

Tips would be treated confidentially, DOC said.