A small dog has been captured on video attacking a protected New Zealand fur seal in North Canterbury.

The dog, described as being and white with ginger markings, was filmed by a member of the public attacking the seal on Pines Beach in Waimakariri on Tuesday morning.

A man, presumed to be the dog's owner, appears to be chasing the dog as it continues its attack on the seal.

DOC/SUPPLIED DOC are asking for information about this dog, which attacked a New Zealand fur seal on Pines Beach in Waimakariri on Tuesday.

Department of Conservation (DOC) biodiversity ranger Anita Spencer said she was appealing to the public for information about the attack.

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"We want to speak to anyone who may have seen the seal being attacked, or the dog and its owner on the beach around the Pines Beach area, mid-to-late morning on Tuesday.

DEPARTMENT OF CONSERVATION A New Zealand fur seal pup.

"We realise this footage is distressing but we want people to understand how easily a dog attack on a seal can happen."

The consequences were almost always bad for the seal, Spencer said.

"The dog in this video is clearly not under effective control and we're disappointed this is yet another dog attack on a seal."

The man eventually got the dog under control and the seal made it back to the sea, she said.

People needed to be more aware that beaches were shared with seals, she said.

Owners should keep their dogs on a leash in areas where seals were present, as well staying a safe distance of at least 20 metres away.

"Seals regularly rest on local beaches and people need to expect them to be there."

Last year three seals were killed by dogs on Christchurch beaches, she said.

New Zealand fur seals, or kekeno, are fully protected.

People with information on the attack, the dog or its owner are asked to call the Christchurch Mahaanui DOC office on (03) 3419100 or the 24-hour DOC hotline on 0800 DOC HOT (0800 362 468).