The slaughter of 23 seals on the Kaikoura coast last week has prompted debate on whether seals need to be culled in the area.

The fur seals, which included eight newborn pups, were found clubbed to death on Wednesday last weekend by Department of Conservation contractors at the Ohau Point seal colony, about 22km north of Kaikoura township.

The president of the Kaikoura Boating Club Ted Howard told Radio New Zealand that while he wasn't condoning the attack, the numbers of the seals had increased rapidly and needed to be managed.

"I moved here full time 12 years ago and there were about 3,000 seals; now there are about 10,000 seals."

Mr Howard said the seals compete for the same fish sought by fishermen.

"Mostly they do eat lantern fish, but if they get hungry, they will eat almost anything," he said. "I've seen them eat blue cod, octopus, conger eel, red cod, barracuda; so they can be in competition with us."

The Department of Conservation's South Marlborough area manager Dave Hayes said seal numbers have increased on the coast, but did not believe they were having an adverse impact on fish stocks.

Mr Hayes pointed to DOC research published in February this year which looked at the diets of New Zealand fur seals.

"Primarily their diet is lantern fish, which is not a target species for fishermen, recreational or commercial," he said.

But fur seals will sometimes eat the species of fish named by Mr Howard, Mr Hayes said.

"They are opportunist feeders - if any of those species swim past them they will eat them."

Mr Hayes would not comment on whether there should be culling but said DOC was working with iwi and fishermen to address their concerns.

Fisherman Richard Craig told Radio New Zealand if the seal numbers increased anymore it could get to a stage where there was nowhere to launch boats into the water.

"You're not supposed to go within three metres of them and you're not allowed to disturb them. That means that if there is only a six-metre gap between seals, it means you cannot pass through that without actually disturbing a seal."

Mr Hayes said the department was aware of concerns about seals hampering the launching of vessels as they often lie on boat ramps. He said DOC was working with boat club members to come up with a protocol so they could move the seals on in a way that does them no harm.

Mr Hayes said the department was continuing to receive leads from the public into who may have been responsible for the brutal attack last week.

"Some have produced some leads we are working though with the police," he said. "To date there has been nothing concrete. But every little piece helps to build the whole picture.

"We are also heartened to hear of the value the vast majority of New Zealanders are showing for seals on the coast and the value they have to tourism."