A New Calamari Counter

Without a point of reference, it is hard to tell whether the market squid (Loligo opalescens) in this image is tiny but close to the camera, or big and far away.

The difficulty lies in the fact that not much is known about the juvenile stages of market squid, despite their being the most fished species off the coast of California.

Louis Zeidberg from the Monterey Bay Aquarium Research Institute (MBARI) has tried to shed some light on the issue.  He has measured 150 squid of various ages and determined a way to calculate the size from the ratio of the squid's eye diameter to its mantle length. 

The mantle is the spotted, tube-like structure to the left of the eye in the image above.  It is sliced into rings for many calamari dishes.

The squid's eyes mature early, so in a juvenile, they will be big for their body.  Eventually, the mantle and other parts catch up to the eyes.

Knowing the size of a squid from the eye-mantle ratio, Zeidberg was able to calculate the speed of squid moving across video images from MBARI's remotely operated vehicle Ventana.

He found that market squid can swim about 50 percent faster than laboratory studies had previously shown.

-- LiveScience Staff

Credit: © 2001 MBARI