A researcher embarking on the country's biggest shark-tagging exercise says New Zealand is lacking scientific data about its rapidly declining shark populations.

Riley Elliott, 27, is part of a generation of shark scientists who are getting in the water with their subjects.

Part of his research is to explore why one tagged shark shot off to Tonga from the Bay of Islands and another four split into male and female groups.

Over the past month, Mr Elliott has tagged five blue sharks with $4000 satellite tracking devices as part of his PhD studies.


Three were tagged in the Bay of Islands and two off Hahei Beach in the Coromandel.

The sharks were caught about 100m from the shoreline and restrained in a hammock while satellite tags were drilled through their dorsal fins and then released.

Now every time the shark surfaces, the location - and other information such as temperature and depth - is sent to satellites that pass every 10 minutes and back to Mr Elliott's computer.

The satellite information has revealed some interesting trends.

Three of the four male sharks have gone north to Three Kings Islands and the female has stayed alone at the top of the Coromandel.

"Sharks are known to separate by sex and by age but nobody knows why yet," he said.

The fifth shark, also tagged in the Bay of Islands, has travelled 5000km in just a matter of weeks, and is almost in Tonga.

Mr Elliott is not able to say whether this is strange shark behaviour because there just isn't enough data collected on them yet. But tracking will hopefully reveal why.

Tagging blue sharks is a first for New Zealand and follows Niwa's tracking of a Mako shark that swam 13,300km to Fiji and back last year.

Next on the list for satellite tagging are great whites, Mr Elliott says, which shark scientists have been doing in South Africa for several years.

"New Zealand is largely lacking in shark awareness, even though we have just as many sharks as other places like Australia and South Africa."

Because of a lack of funding for shark research, Mr Elliott has had to fundraise to buy the six $4000 satellite tags and pay $2000 a year to the satellite company that tracks them.

But he says the information is crucial and the more people know about sharks, the less they will fear them. Especially since the death of shark attack victim Adam Strange at Muriwai Beach two weeks ago.

Fear and misinformation have meant that their current crisis in numbers is being overlooked by the New Zealand public.

"Presently, there is a global crisis of shark populations with 100 million to 240 million sharks killed each year for shark fin soup. New Zealand has no scientific data to assess population size yet it's legal to fish for sharks."

Mr Elliott will be heading out to tag the last blue shark this Easter, and hopes the data beamed back to his computer will shed some light on what motivates shark behaviour.