UPDATED 8.40am: Calls for more observers onboard fishing vessels, as a ban on shark finning in New Zealand waters comes into effect.

New Zealand is currently one of the top 20 exporters of shark fins to Hong Kong.

Conservation Minister Nick Smith says [told Susan Wood] shark finning's doing a lot of damage to New Zealand's reputation and the industry has come on board.

"About 30 percent of sharks species globally are at threat of extinction.

"They're a very slow growing species and that's where the fishing industry recognises that the few dollars they get from selling the fins is simply not worth it in the big picture."

NZ Shark Alliance spokesperson Melina Palka says having adequate observer coverage on fishing vessels is the only way to ensure they comply with the ban.

"Whether that's independent observers or electronic monitoring systems, that is really what's going to be needed to be ensured these strategies are being followed in good faith and not being exploited or abused."

Palka says some fleets are proactively working toward this, but success will depend on resourcing for electronic monitoring systems and government allocation of observers.

She says the industry will need to make a decision whether to move toward releasing sharks alive or start exploring other uses for them.

"Whether it's the sharks' livers or if there's markets for their flesh - they're going to have those two options."

Melina Palka says conservation groups hope the majority will choose to release sharks alive.