Where have all the sharks gone? Scientists want to know

This summer, the Department of Conservation (DOC) is encouraging us all to be citizen scientists and share sightings of protected marine species.

There are nine protected fish species under the Wildlife Act, including the basking and great white sharks, rays and two types of grouper - so, if you are fishing, diving or boating, they really want you to keep a lookout.

DOC marine technical advisor Clinton Duffy told Afternoons on Friday they always wanted to hear about sightings of rare species, but were hoping for more this summer than before.

"Marine megafauna, including whales and large sharks and rays, they used to play an important role in most of our marine ecosystems. And their removal has certainly changed the way those ecosystems function and change the way energy flows through marine ecosystems… So yeah, it does make a difference.

"Of course, many of these things disappeared long before we had a good understanding of marine ecosystems and, you know, the loss of large predators… the effect of that still has to be studied in-depth."

The protected species under the law were:

"We'd love to know when and where they saw it and the estimate of how big the animal was would be great," Duffy said.

"And if possible, some photographs. I mean, a lot of people have GoPros these days and a GoPro on a stick can get good underwater photographs."

It’s simple number eight wire thinking. (Source: 1News)

Some individual fish - such as manta rays - can be identified by their unique patterns.

"We're able to sort of get good sightings of them over the years where it's able to determine if the animals are coming back to the same places, potentially where they go as well…

"We're not necessarily going to roar out there straight away and try to find it, but the sightings will help us identify what the important habitats are for these species, you know? Where they are occurring, the times of year they're there and what important habitats may be for them, which all helps us work out things - like how often are these things interacting with fisheries? Where might they be interacting with other sorts of activities like, you know, tourism and commercial shipping, that sort of thing."

Duffy said he would be most excited to receive reports of basking sharks.

"The last confirmed sighting of one of those in coastal New Zealand waters was around 2012, and that was only a single animal… These things used to form schools of several hundred and surface in summertime, so I think I would be pretty excited to hear even of one of those in coastal waters."

Their absence was possibly a result of climate change's effects on plankton, which basking sharks eat. Overfishing is also a problem, particularly for large marine animals, which like humans can be long-lived and reproduce slowly.

"Manta rays, for example, only produce a single pup every time they give birth, so they're very, very sensitive to overfishing and exploitation."

To report sightings, go here or call 0800 DOC HOT (0800 362 468).

"It's particularly important that people call that number in the case of a stranding or an accidental capture of one of these species," Duffy said.

For sharks specifically, send photos or video to [email protected].

rnz.co.nz