With the warmer weather here to stay, an increase in shark sightings is expected over the summer period.

Department of Conservation marine scientist Clinton Duffy said the right conditions would mean more reports about shark activity.

"There probably won't be any more sharks than there normally is, they will just be more visible if we get calm weather."

He said people could expect sightings of many sub-tropical species, as well as great whites as there was a semi-resident population in New Zealand.

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"They spend most of the summer here, arriving in November/December, before the adults leave in July/September", Mr Duffy said.

The creatures' movements - particularly those of mako sharks, blue sharks and thresher sharks - were very much dependent on water temperatures, and whether or not there are prolonged periods of onshore wind, which blows more oceanic water close to shore.

During spring and summer, sharks were more abundant and found in greater variety around New Zealand waters.

In winter, sharks moved away from the coast and to deeper offshore waters where temperatures were more stable.

He noted "high-risk" places included out the back of the surf break on beaches, areas near deep channels, around concentrations of bait fish, and near seal colonies.

From the twilight period through the night is typically the time when sharks were feeding and likely to be most aggressive, he said.

He emphasised people should not be scared of sharks but should instead take "sensible precautions".

"When you are in the water, it always pays to have in the back of your mind that there might be sharks around but the risk this year will be no greater than any other year.

"Most people should be focused on general water safety rather than worrying about sharks at the beach."

Similarly, Orca Research Trust founder and principal scientist Dr Ingrid Visser said orcas were expected to be sighted as normal.

"They are wild animals, so it is difficult to predict.

"There are fewer than 200 orcas living around the whole of New Zealand. At anyone time there might be 20 orcas in the Hawke's Bay area.

People have to remember the law," she said. "They are not legally allowed to approach the animals closer than 50 metres.

"Remember wildlife are protected and people must give the animals the respect that they deserve."

She said orca sightings should be reported to 0800 733 6722 (0800 SEE ORCA).