A shark which tried to eat another hooked on a fishing line has become a worldwide sensation even though experts say the image of the encounter shows a common experience for anglers.

Graphic designer Bryony Grover captured the image of the blue shark trying to eat a school shark while 14 kilometres off Tasman Bay, at the top of the South Island.

The image went viral online and has been picked up by media around the world. The United Kingdom's Daily Mail inaccurately called it a great white shark and said it showed "Charles Darwin's survival of the fittest - or perhaps biggest - theory in action".

The shark was identified by expert Clinton Duffy as a blue shark, of about average size and a common sight in coastal and ocean waters around New Zealand.


Ms Grover said she became aware of it after a few smaller school sharks - like the one pictured on the line - began mooching around the boat. Ms Grover, on holiday from Melbourne to her Nelson home, watched it cruising back and forth beneath the surface while out fishing with friends Dave and Kate Everton.

"I've never seen one in the wild," she said. "I'm quite fascinated by them."

When the school shark in the image was hooked up and drawn close to the boat, the blue shark swam in for a closer look. "He was slowly trying to grab it. It wasn't scary-scary. It was pretty non-aggressive."

After a few bites around the tail, the school shark was brought aboard while the blue shark submerged. There was debate about its fate - "If we bring it in, it's going to die. If we throw it back, it is going to get eaten. We threw it back. It sunk out of sight."

The shark was one of about five caught during the two-hour trip before returning to shore when the weather turned rough. The anglers also caught four blue cod, the initial target for the trip.

Mr Duffy said the image showed the challenges anglers faced. "It is a pretty common occurrence. It's a pretty average sized blue shark - one of the most abundant sharks in the world."

- NZ Herald staff