With 'unusually warm' sea temperatures, shark sightings are expected to increase this summer

With "unusually warm" ocean temperatures being recorded in many parts of the country, there could be an increase in the number of shark sightings this summer.

However the jury is still out on whether that is because there are more people out in the water to spot the sharks or whether there really are more of the ocean predators swimming around our waters.

On Thursday a woman died in a suspected shark attack at Waihī Beach. Surf lifeguards said shark sightings were "very common" in the area, and that warm waters had recently brought more sightings than normal at the beach.

A dead bronze whaler shark also washed up on Auckland's Milford Beach on Thursday, surprising locals.

NIWA shark expert Warrick Lyon told Newshub warmer sea temperatures often brought more sharks to New Zealand waters, as a number of species - such as tiger sharks and whale sharks - "follow the warmer currents from the Pacific or Australia".

"There are certain species of sharks that just prefer warmer temperatures," he said.

And temperatures have certainly been warmer over the past week. NIWA meteorologist Chris Brandolino said in some parts of the country the ocean has been "most unusually warm" over the past seven days.

"Basically off the North Island overall ocean temperatures are most unusually warm at the moment for the time of year," Brandolino told Newshub.

"And I would expect ocean temperatures will remain above average if not more unusually warmer-than-average over the next week or two."

He said the warmer temperatures would most likely continue for a while yet, thanks to La Niña.

"Typically when we have a La Niña in our neck of the woods that favours warmer-than-average ocean temperatures in and around the New Zealand region. So that's something that would favour warmer-than-average ocean temperatures for the summer season and summer into early autumn as a whole."

But despite the link between sharks and warm water, Lyon said it's hard to definitely say if overall numbers are up.

That's because while some species flock to the warmth, others leave our shore to head south to cooler waters.

"There's a natural ebb and flow of population numbers," he said.

But since we can't "count them like sheep on a farm" it's not possible to know for sure how many more there are when water temperatures heat up.

"There might be more sharks but we don't know."

Whether actual numbers are up or not though, Lyon said the summer months definitely bring more shark sightings. One reason for that, he said, was that there are simply more people out in the water.

"We don't know if the numbers are changing. My view is that there's more people out looking and more people have phones and they take pictures and videos [of sharks]," he said.

Following the death of the woman in Waihī, Surf Life Saving New Zealand eastern region lifesaving manager Chaz Gibbons-Campbell told Newshub that despite an increase in sightings at the beach, it was extremely uncommon for an attack to take place.

"These attacks are very rare and few and far between," he said.

Lyon's advice to anyone who sees a shark was to stay calm and "just admire them - that they're part of our ecosystem".

"They are our biodiversity and having them is essential. It's part of a healthy marine ecosystem."