Mako shark tag found on 90 Mile Beach

The mako shark being tagged in New Caledonia, and (inset) the tag (top) found on 90 Mile Beach.

It was appropriate that it was Clare Veltman who found a shark tag on 90 Mile Beach.

A "wildlife scientist" by trade, she had just begun her Te Araroa experience when she spotted the tag and put it in her pack.

"I knew what it was, and immediately thought about the person waiting to get the data it holds. So I decided to do something about it once I got to Kaitaia."

The tag, described as looking like a large fishing lure with an antenna, marked with the manufacturer's details and a serial number, had been attached to a mako shark by Niwa as part of a Pacific-wide study, contracted by the Western and Central Pacific Fisheries Commission, to measure the survival rate of mako and silky sharks returned to the sea by commercial longline fishers.

The study is aimed at determining whether the way sharks are caught and released makes a difference to their survival.

Niwa shark researcher Warrick Lyon was excited to get the tag back.

"This is the first tag out of 75 that have been deployed that has been returned to us since the study began in May last year.

"It provides us with really detailed information that we wouldn't otherwise have," he said.

The tag had been attached to a 2.5m mako shark by a fisheries observer aboard a tuna longline vessel off New Caledonia on July 3. The shark was then released, and swam to New Zealand.

A steel pin in the tag was designed to corrode after 60 days, allowing it to float to the surface from where it began broadcasting data to a satellite system. By the time that happened the mako, the fastest-swimming shark species, was well inside New Zealand waters.

"The information we get from the tags includes a daily report of minimum and maximum water temperatures, and maximum depth of the shark while the tag was attached," Mr Lyon said.

"If we get the tag back, we can retrieve much higher-resolution data at 10-minute intervals. That level of detail is far more valuable, and very exciting."

Mr Lyon said Niwa knew sharks travelled north from New Zealand to the Pacific Islands, but there was little evidence to show that they also swam back.

"This will build on information we already have and help us establish more about how these sharks use the ocean," he added.

Meanwhile, Ms Veltman spent the $200 reward she received for returning the tag on a new sleeping mat.

Mr Lyon said at least one tag was still to be found at Lottin Point, Cape Runaway, still waiting to be found.