Higher than normal numbers of skinny and emaciated fur seals, or kekeno, are being found dead along the east coast of New Zealand, the Department of Conservation (DOC) says.
DOC marine advisor Laura Boren said staff had received an increased number of fur seal call-outs over the winter, mainly about sick or dead fur seals, and have noticed increased pup mortality at breeding colonies including Kaikoura and Otago.
Ms Boren said it was highly likely this was a result of reduced productivity and prey availability, which could be related to a number of factors.
Tests will be carried out on a selection of pups to confirm the cause of death. The department is gathering information to understand the extent of the situation and will continue to monitor it.
"It's usual at this time of the year for newly weaned young fur seal pups, aged nine or ten months, to start showing up on our beaches. They're just learning to make it on their own and its normal for many to be emaciated and weak.
"Unless a seal is being harassed by dogs or people, is entangled in marine debris, is severely injured, or is in a situation where it might pose a risk to itself or to people for example, on a road or in a backyard, the best policy is to leave them alone."
Ms Boren urged dog owners to control their pets around seals.
"These weak and helpless seals occasionally turn up in public places where they are vulnerable to dogs. The seals are small and easily picked up and shaken by a dog. Last year, several seals were killed by dogs," she said.
"A dog owner whose dog attacks a seal could face prosecution and their dog could be destroyed.''
Anyone charged under the Marine Mammals Protection Act with harassing, disturbing, injuring or killing a seal faces a maximum penalty of two years' imprisonment or a maximum fine of $250,000.