The Invasion of the Diablos Rojos: Humboldt Squid

MEXICAN fishing fleets call them diablos rojos, or "red devils" - and when Stanford University graduate student Julie Stewart wrestles the first Humboldt squid aboard our research vessel, the Fulmar, in California's Monterey Bay, it becomes obvious why.

This beast is angry, and has flashed from white to a deep maroon. It's nearly 1.5 metres long, including the tentacles, which flail in Stewart's hair until she can offload the catch into a cooler filled with seawater. That only gives the squid ammunition, as it can now fire a powerful jet of water and ink at anyone who strays into its sights.

"Ink in your eye stings," warned Stewart earlier. She is also careful to avoid the animal's sharp beak, which can deliver a nasty bite. Within a minute or so, Stewart and her colleague John Field of the US National Oceanic and Atmospheric Administration have attached an electronic device to one of its fins. It's time to return the devil to the depths.

We are out on the Fulmar on this bright December day to learn about the animals' movements. When the device detaches and surfaces, it should send a radio signal to reveal its location, and transmit data revealing how the animal has been migrating up and down in the water. This is key to understanding why the Humboldt squid (Dosidicus gigas) has invaded the waters off central California, and how it may affect the region's valuable fisheries.

While the total size of the invading horde is still unknown, observations from autonomous submersibles and sonar indicate that they often swim in dense schools of at least 100 individuals. "We've seen densities as high as eight per cubic metre," says William Gilly, Stewart's supervisor at Stanford's Hopkins Marine Station in Pacific Grove.