How to measure a shark

Q. How do you measure a live, free-swimming shark? A. From a distance.

Sounds obvious, doesn’t it? You can’t easily swim up and lay out a tape measure alongside them from snout to tail. But with all the tricks of light bending on its way through water and air and the inevitable BIG FISH tales, how can scientists make accurate estimates of shark size? (And before you ask, shark body size is an important part of studying the health of shark populations).

There’s a new handy gadget that does just that – and it looks pretty cool too:

It’s the brainchild of a project  funded by Save Our Seas Foundation and led by Dr Mark Meekan of the Australian Institute of Marine Science and Gabriel Vianna of the University of Western Australia. They’ve been trying it out at popular dive sites in Palau. Here’s an excerpt of an article from Save Our Seas revealing how it works:

Paired video cameras in housings film the sharks and a diode (light) in the front of the cameras allows the researchers to synchronize frames of the video.

Using principals originally developed for aerial photography, these researchers are then able to calculate the length of any body part and total size of the animal with a precision of a few millimeters. The technique is so accurate that the researchers can recognize individual animals by their body proportions. By repeatedly filming the same animals over a number of years, they will be able to measure growth rate of these sharks.

Read in full here

Image: (c) Save Our Seas Foundation / Peter Verhoog