Marbletail, a 4.1m shark named after the colour pattern on his tail, dominated the other sharks in the tagging area, scaring them away and, as a result, only 23 sharks were tagged, down from 41 the year before, Niwa principal scientist Dr Malcolm Francis said.
Niwa, Department of Conservation and Auckland University researchers recently completed their annual tagging trip around Edwards Island to investigate if the sharks are resident or transient and the size of the population.
"It became much harder to tag new sharks as the trip went on."
For the last six years, the scientists have been travelling to the waters off Stewart Island to tag the protected great white sharks and take identification photographs.
"We saw many of the same sharks that we have tagged in the same place in previous years. Some of them are local identities that have become well known to us," Dr Francis said.
This year, the group used acoustic tags, as well as pop-up tags, to provide information showing where sharks go within a few hundred metres by sending out a coded pinging sound unique to the shark.
Data loggers, deployed on moorings around northeast Stewart Island and Ruapuke Island, would pick up the pings and would be left for two years.
The information would be downloaded at intervals of three to six months.
The pop-up tags were used to track the sharks' movements to the tropics each year and recorded depth, location and temperature for about a year before "popping up"and transmitting data to scientists through satellite.
Doc scientist Clinton Duffy said all those sharks tagged last March left Stewart Island by mid-June to mid-July, heading 2500km to tropical islands north of New Zealand.
"Last year, we estimated that around 100 sharks were in the region at some time over the past three years."
Once they went through the footage taken on this year's trip and identified and counted each shark, they would be able to refine that estimate, he said.
"So far, it looks like it will be higher than last year's estimate."
