William Gilly, a mollusk specialist at Stanford University's Hopkins Marine Station in Pacific Grove, is trying to find out whether domoic acid affects squids at all. The answer is worth finding out for several reasons, Gilly said: It could affect the fishing industry. There is a possibility that people might ingest the dangerous, sometimes deadly, toxin while enjoying a squid platter. And squids are important to the rest of the ocean and the food chain. They eat smaller animals and are eaten in turn by whales, dolphins, fish and birds.

"The squid population is important because it's a major player in the ecosystem of the ocean," Gilly said. "It's important to learn more about what affects squid and makes them have strange behaviors."

The state Health Department tests Monterey Bay regularly for domoic acid levels. Earlier this year, there was enough domoic acid in Monterey-area waters to close down the sardine fishery, according to the state Department of Fish and Game.

Domoic acid doesn't affect sardines, but the fish carry it in their intestines, potentially affecting people who eat them. The toxin causes a disease called amnesiac shellfish poisoning, which can cause permanent brain damage and death.

Domoic acid produced by one species of diatoms (microscopic organisms that float in the ocean) races up the food chain from diatoms to fish to big mammals such as sea lions and dolphins. The naturally occurring chemical comes and goes, and no one is sure what makes diatoms produce it.

Nor does anyone know how many 2-foot-long squids made up the 14 tons of flesh along San Diego's coast in late July 2002. Jumbo flying squids are native to waters off Baja California and only come as far north as San Diego once every few years. This year there are schools in the ocean off of Monterey, and some years they get as far north as Oregon.

Squid authority Eric Hochberg, a curator at the Santa Barbara Museum of Natural History, has been hunting for clues to the mass mortality. He's pored through historic photographs and records that date back 200 years in his search for evidence of past strandings of the jumbo flying squids, which can grow to be more than 10 feet long. His search has turned up nothing.

"There is nothing that I had information on that was as massive a stranding or mortality event as occurred in La Jolla in July," he said. Hochberg said he doesn't know why the squids stranded, but domoic acid is a good possibility.

The first known domoic acid outbreak was in eastern Canada in 1987, when 3 people died and more than 100 were sickened after eating mussels contaminated with domoic acid. This spring, diatoms produced huge amounts of domoic acid in California waters, more than has ever been recorded, said John Heyning, a marine mammal biologist at the Natural History Museum of Los Angeles County.

Almost 100 whales and dolphins beached in Southern California because they had domoic acid poisoning, Heyning said. Of the whales that beached in Southern California, 3 were Cuvier's beaked whales, which are known to eat jumbo flying squid. Heyning is leading a National Marine Fisheries Service investigation into the marine mammal beachings.

Nobody knows whether domoic acid can make squids sick. That's what Gilly, the Stanford biologist, wants to find out. "Squid have receptors in the nervous system that are a target for the domoic acid. So if it can get into the squid nervous system, it could cause a problem," Gilly said. Gilly has one of his graduate students at Stanford testing how market squid, a different species from jumbo flying squid, react when domoic acid is placed on a neuron in its system.

The one type of neuron tested indicates that squids are sensitive to domoic acid, but less sensitive than mammals, he said. But, he said that squids could have a half dozen other receptors that no one has looked at yet.

"But what it does in the blood of a living squid, we don't know," Gilly said, but surmised that the toxin could interfere with motor control. That might make the squids clumsy in the water and more prone to beaching. He said he wants to feed toxic krill to squids in the lab to find out how it affects them.

There are several other possibilities for why the squids beached, said Hochberg, the Santa Barbara curator, but none seems any more likely than domoic acid. One theory is that the squids were following grunion, a fish that comes up onto the beach to spawn. It is probably the culprit in several smaller beachings, Hochberg said, but most of the squids he dissected had empty stomachs.

Disease was another possibility, but the squids didn't look sick, he said. "From all of the animals that I've looked at, there's no gross pathology that you'd say they have some contagious parasite or some problem," he said. Some researchers suggested that dolphins herded the squid onto the beach, but Hochberg said that most dolphins "would not handle squid that are as big as these are. So I have my doubts on that."

On the other hand, if it was domoic acid, sea gulls should have died from eating squid on the beach. Sea gulls were eating the squid, but no one has reported unusual bird deaths. If scientists know what caused the beaching, they can find out how to keep it from happening in the future, said Greg Helms of The Ocean Conservancy in Santa Barbara.

"Were they poisoned or somehow damaged by something out there and, if so, what was it?" Helms said. "Or is it just Mother Nature doing her thing?"

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