Auckland-born marine scientist Stephen Lyon is an unlikely candidate for the job of creating the world's largest shark sanctuary - he has had a crippling fear of sharks since age 5.

As fishermen from his Cook Islands home increasingly report dwindling shark numbers, the University of Auckland-educated Mr Lyon has proposed an ambitious conservation project.

His charitable trust Pacific Islands Conservation Initiative wants to see the Cook Islands' entire Exclusive Economic Zone (EEZ) made into a sanctuary for sharks and rays, a project that would increase protected areas for sharks worldwide by 50 per cent.

A sanctuary would stop commercial fishing of all shark species within a 2.3 million square kilometre region of the South Pacific, a space 10 times the size of New Zealand's landmass.

Mr Lyon, 38, told the Weekend Herald from his dive company office in Rarotonga that shark conservation was not an obvious fit for him given his childhood phobia.

 "When I was 5 I saw the movie Jaws.

"That put a huge amount of fear into me for sharks. I was paranoid to the point that I couldn't swim in a swimming pool at night because of a subconscious fear.

"I still have a feeling of anxiety when I roll into the water on every dive I do, until I orient myself, look around and see there's nothing there.

"But I've got a much more pragmatic and conservation-oriented approach now. I think sharks are exploited and it's to the point now where coastal-dwelling fishermen notice the difference."

Of the 18 recorded shark species in Cook Islands waters (the true number is believed to be around 30), 13 were listed as threatened, and five of them were endangered or vulnerable.

The sharp decline in shark populations was driven by a growing appetite for shark-fin soup, a delicacy which the quickly growing middle class in China have developed a taste for.

The Cooks has no commercial shark industry.

But it also has no catch limits or rules against shark finning, which meant Fijian, Chinese and Taiwanese fishing boats loaded sharks from South Pacific waters on to factory vessels and shipped their catch back to Asia.

The high value of the fins, which can fetch up to US$1280 a kg, meant illicit trade in shark fins was rife.

The global blackmarket in shark materials is reportedly second only to the illegal drugs trade in terms of revenue.

Mr Lyon said the sharks are often crudely "finned" - a messy, bloody process which usually lead to the rest of the body being dumped back into the sea.

To create a protective sanctuary, the Cook Islands Government would have to outlaw commercial shark fishing, ban retention of sharks as bycatch, and ban sale or trade of any shark material.

The trust admitted that policing the entire EEZ would be a difficult task for the tiny island nation.

But Mr Lyon was optimistic his project would gain traction because Polynesians had a strong cultural connection to sharks.

The fish appear on banknotes, islanders' tattoos and commonly feature in Polynesian imagery.

The Cook Islands Prime Minister and Minister of Tourism have privately backed his trust's project, but Mr Lyon and programme manager Jess Cramp want to be sure that they have the support of the islands' 18,000 inhabitants.

If the sanctuary is established, the Cook Islands will join Palau, the Maldives, Tokelau, the Bahamas, Honduras and the Marshall Islands as nations who have reserved their waters as a safe haven for sharks.

The sheer scale of Mr Lyon's project would dwarf those projects.

But it will only happen, he said, if he could destigmatise the portrayal of sharks as fearsome man-eaters.

"All we see is the sharks when they come ashore, with big teeth and the killer's eye. People have never seen a shark underwater - they are quite timid and nervous.

"In one of the atolls in our northern group ... we've sat there and watched tiny, baby sharks swimming around the feet of kids playing in the water ... it's fantastic."

Fin soup fans bite into ocean population

Demand for a shark fin-flavoured broth served at weddings and special events is the primary cause of plummeting shark populations worldwide.

A report published by the Pew Environment Group this year said 73 million sharks were killed every year, primarily for their fins.

This overfishing upsets ocean ecosystems which depend on the apex predators for balance.

The shark fins are sold to upmarket restaurants in China, Hong Kong and Japan.

The controversial shark fin dish is also found on menus in New Zealand.

Grand Harbour restaurant, in Auckland's Viaduct, offers shark fin in brown sauce for $100 a person, or sauteed shark fin for $300. Conservation group Forest and Bird has called for customers to boycott restaurants selling shark fin dishes.

Shark finning is outlawed in New Zealand waters if the sharks are still alive.

The popularity of the delicacy could be waning. Last month, the prestigious Asian hotel chain Peninsula banned the dish.