The Department of Conservation is working with police to investigate the deaths of 19 fur seals.
Necropsies on eight adult seals revealed they had been shot while the cause of death could not be determined for the other 11, which included one pup.
Te Rūnanga o Kaikōura and DOC first appealed for information on 5 November about the deaths of five adult seals at Half Moon Bay and another six seals at Ōhau Point, north of Kaikōura township. Since then, another eight seals - one a pup - were found dead several hundred metres north of Half Moon Bay.
The seals were believed to have died within the last month.
The department's South Marlborough operations manager, Phil Bradfield, said all the deaths were suspicious.
"It's disturbing and deeply disappointing to know someone has deliberately shot and killed at least eight fur seals," he said.
"Te Rūnanga o Kaikōura and DOC take very seriously any harm to fur seals which are a taonga and legally-protected species.
"We're hoping people will come forward with information to help us find whoever is responsible for the heartless shooting of at least eight of the seals."
It was not been possible to closely examine the six dead seals in the Ōhau Point Fur Seal Sanctuary because it would disturb pregnant females and young pups in the breeding colony, Bradfield said.
Seals had been re-establishing on the Kaikōura coastline after the 2016 earthquake damaged parts of their habitat.
The penalty for harassing, disturbing, injuring or killing a marine mammal under the Marine Mammals Protection Act 1978 was a maximum sentence of two years' jail or a fine of up to $250,000.
Anyone with information about the seals' deaths should call DOC's 24-hour number 0800 DOCHOT (0800 36 24 68) or Kaikōura Police via 105 and quote file number 211103/1981.
Information could also given anonymously through Crime Stoppers on 0800 555 111.
