LA PAZ, Mexico — I STAND on the deck of the boat with a tank of air on my back, a weight belt around my waist and images of space aliens swarming my mind.
Beneath me prowl thousands, perhaps millions of creatures that might as well be from another world -- voracious animals with probing arms and tentacles lined with hundreds of gripping suckers and clasping hooks, and with beaks designed to tear off fist-sized hunks of flesh.
Marine biologists have a lot to learn about the Dosidicus gigas, a.k.a. Humboldt squid, or jumbo squid. What they know is that these cephalopods can reach lengths of 7 feet and weigh as much as 100 pounds, that these torpedo-shaped mollusks thrive at great depths and use a form of jet propulsion to squirt themselves quickly through their hazy realm, and that they're extremely strong and agile.
"Dosidicus is the Arnold [Schwarzenegger] of the squids, for sure," says William F. Gilly, a professor of biology at Stanford University's Hopkins Marine Station. "They are the most powerful squid and have quite the armament for dealing with big prey: thousands of rings and sucker cups. Yet to see them feeding on the little fish in the wild is really interesting. They reach out so delicately and grab them as though they're eating snacks at a cocktail party."
Long common off South America, they began establishing themselves in the Gulf of California -- better known as the Sea of Cortes -- in the 1970s. Now their growing numbers and intriguing behavior have scientists stumped. At the moment, I'm waiting for a deckhand to haul into view a squid he's hooked with a hand line. With it will come others, he assures me, because these are cannibals, quick to sense trouble among their own.
"Some assurance," I mutter. I try not to think about the stories I've heard, notably one in which this same species in this same general area turned an Arizona marine biologist's dive into a scene from a bad horror movie.
New sea stars
Jacques Yves Cousteau once described the southern Sea of Cortes as the Galapagos of North America. For years, divers mingled wide-eyed beneath the enormous schools of hammerhead sharks that gathered over seamounts. Sport fishermen waged epic battles with marlin, tuna, swordfish and sailfish.
But over time, subsistence fishermen tossing spark plug-weighted hand lines from skiffs, leathery gringos living out Hemingway fantasies, and, most significantly, commercial boats setting monofilament nets and lines with baited hooks, depleted the number of fish.
Now, only old-timers can remember when an angler could look out over the water and see tuna leaping for miles and crowds of marlin and sailfish sunning on the surface.
Sharks, in particular, have suffered. Carlos Villavicencio, a professor of marine biology at the University of Baja California Sur in La Paz, says that his interviews with fishermen suggest that the number of sharks caught has dropped by about 40% since 1990.
Mexico has, over the years, more forcefully regulated fishing and now has a 50-mile exclusion zone to keep large-scale commercial fishing well offshore. But it continues to allow the limited use of drift gill nets and long-lines inside the zone, and inside the gulf as part of an experiment to gather data before publishing a new shark norma, or regulation.
Meanwhile, over the last three decades, the fast-growing, short-lived Humboldt squid, has been making long seasonal visits in numbers that seem to be growing. And in recent years, particularly in the Santa Rosalia and Guaymas areas north of La Paz, they've taken up year-round residence, feeding largely on lanternfish, small, deep-sea creatures that rise to shallower depths at night -- which is when squid feed.
Is the Sea of Cortes squid invasion a sign that one of the richest marine areas of the world is ailing? Commercial fishing frequently cuts the overall age of species in an ecosystem, says Gary Thomas, a professor of fisheries ecology at the Rosensteil School of Marine and Atmospheric Sciences.
So it makes sense, he says, to assume that in the gulf, heavy fishing of once-stable populations of long-living finned fish would lead to "rapidly changing, highly fluctuating stocks of short-lived species, such as squids."
That, he adds, probably explains why some of the world's most overfished coastal waters -- such as those off Japan -- are dominated by squid.
Some scientists suggest a link between the squid surge and the decline of large predators -- and they note other possible ripples across the ecosystem. What will the effect be on the lanternfish population, for example? And is there a connection to the appearance of more toothed whales in the gulf?
"As squid are lacking predators in large numbers, they are growing very large, which is attractive to sperm whales," says Juan Pablo Gallo Reynoso, a marine mammal researcher based in Guaymas.