Alan Pasiano had spent a quarter century on or below the water before he struck gold. He'd worked diving for abalone in small towns on the pointed western elbow of Mexico's Baja peninsula, fished for tuna on big ships in the Pacific, cooked sea turtle on a cargo boat in Panama, and welded the hulls of oil tankers for Mexico's state-run oil monopoly, Pemex, in Rosarito. But it wasn't until the '80s, when he started diving for urchin, that he got rich.

The late 1980s were the height of the urchin bonanza in the port of Ensenada on Baja's northern Pacific Coast. Japan's economy was booming, but its native stocks of urchin had been wildly overharvested for their gonads, uni. In the waters off Baja's northwestern coast, urchin was still abundant, and the Mexican government had yet to set restrictions on divers, who had realized there was a fortune to be made in peeling urchins from the sea floor and selling them to eccentric buyers from across the Pacific.

In the course of a decade, Pasiano went from being one of the best divers around to running a successful urchin-harvesting business that earned him $3,000 a week. At the peak of his prosperity, he employed eight divers, each of whom could extract as much as 175 pounds of urchin per day. When Ezequiel Hernandez, a prominent personality in Ensenada's seafood trade and food scene, started exporting urchin in the early '90s, he bought the bulk of his product from Pasiano. He was, in Hernandez's words, "un zar de erizo," a little urchin czar.

Today, the little czar holds court at his food cart, the only one in town that specializes in urchin. Stationed on an obscure corner surrounded by mechanic shops and gas stations, Pasiano has made a new name for himself as one of the city's best street vendors and storytellers, a living cautionary tale about urchin, drugs, and greed.

Now sixty-seven, Pasiano is a giant, tall, and wide and expansive when he talks—which he does, at length. His thick hands are encased in leathery skin, fingers permanently bent, the calluses of several different lives built one atop the other. "Money is a swamp," he told me when I visited his stall back in January, before I'd even had a chance to order my tostada and cocktail. "You put one foot in, and little by little," he said, raising his hand up slowly past his eyes, "then you sink up to here."

In Baja, urchin had always been a fisherman's snack, a ubiquitous pest good for spreading on a tostada, but not much else. That changed in the 1970s when the Japanese started buying Mexican uni in bulk. Japanese immigrants had lived in Ensenada since the beginning of the twentieth century, when they'd crossed the Pacific to work as small-scale fishermen. During the dark days of the Second World War, many were forcibly relocated to inland cities and internment camps, but the majority came back when the war ended. As the economy back home started to grow, Japanese fishermen became traders, focusing first on abalone and lobster and then, as stocks off the coast of Hokkaido began their precipitous decline in the early 1970s, sea urchin. By the mid-1980s, Baja's yields had increased enormously, reaching a peak of 8,500 metric tons in 1986. In those early days, when prices were still set entirely at the daily auctions in Tsukiji, Tokyo's immense wholesale seafood market, Mexican urchin sold for an average of about $40 per pound.

When Pasiano started diving for it in the '80s, red sea urchin (Strongylocentrotus franciscanus) blanketed the sea floor. "We were fishing for urchin—you could really say pirating—anywhere we wanted," Pasiano told me. "You didn't need permission or anything." Back then, he recalled, it was common to see pickup trucks around town with their beds piled with urchin, virtually all of it bound for Japan. Even today, with markets for uni developing worldwide, Japan consumes some 80 percent of the world's sea urchin, and 90 percent of what's produced in Mexico. The 8,500 tons harvested in Mexico's best year represented a fraction of Japan's total intake—these days, the largest suppliers are Japan, Chile, and Russia, trailed by the United States and Canada—but for divers like Pasiano, it was an immense windfall.

When he started his own company in 1988, Pasiano traded the manual labor of diving for endless hours in the processing plant, working through the long nights to extract the urchin roe, break down blocks of ice, and pack it for transport to California. Pasiano had his first taste of cocaine on one of those long nights, when a local pusher approached him to see if he needed a little extra energy. "Once I'd started, I couldn't stop," he says now.

Even as his new hobby became a habit, Alan worked hard. He lived modestly and provided a good life for his wife and kids for years. His biggest extravagance in those years was a trip to Japan with his buyers. But while cocaine didn't kill Pasiano, it did eventually nearly destroy his life. He managed to keep his addiction a secret for years until, in 1994, one of his daughters saw him using. His family tried to intervene, but by then it was too late. In 1995, two years after global landings of sea urchin peaked at over 19,000 metric tons, Pasiano's world fell apart. There was no dramatic collapse. He simply ceased to be himself.

"My behavior, it wasn't normal," he says. "I'd always been such a hard worker, and one day I just didn't want to go back, so I just left." One of his partners stepped in to fill his place and business chugged on, leaving Alan, its erstwhile don, in the dust. Over the next five years, Alan lost his children, his wife, and $70,000 in savings. He lost his home and a quarter of his body weight. He was, by the end of the decade, emaciated, living on the streets, and still addicted.

Urchin populations were wasting away, too. By 2005, average annual yields in Baja were a quarter of what they'd been just twenty years before. According to Cuauhtemoc Rodriguez, who's worked in the urchin trade for almost thirty years, red-urchin densities have dropped from 7.2 organisms per square meter in the early 1990s to just 2.2 today. The government started cracking down on overfishing in the late 1990s, and there are now regulations in place—a six-month diving season, minimum size limits on the catch, a freeze on the number of diving permits—but it may be too little, too late. If population densities drop any further, Rodriguez says, "the system will collapse."

But the pressure to dive and collect and sell urchin is only increasing. With declining yields around the world and growing markets in both Korea and China, prices have stabilized (they're no longer decided entirely by the Japanese market) but also reached a point of absurdity. For most of the year, a pound of Mexican urchin sells for about $30 at Tsukiji. In December and January, around the New Year, the auction price can reach $60. American urchin sells for even more, and prices for what remains of the Japanese stock are astronomical.

In 2000, Pasiano entered an evangelical-Christian rehab program where, over the course of a year, he found God, dropped drugs, and came back to sea urchin (in that order). He used his remaining connections in the industry to get fresh product in the mornings and started selling it to locals out of a backpack. "For all the people diving for urchin, there was no one selling it—not even a single street cart," he told me. By 2004, he'd earned enough money to start a small restaurant in the center of town, but the rent was too high for him to manage, so in 2006 he closed shop, borrowed his sister's truck, and came here to sell his urchin at the industrial fringes of the city.

The urchin that Pasiano gets is as fresh as it gets, usually straight from the sea that morning, though it's also not of the same quality as what you'll find in Japan. It's darker in color—a deal-breaker for Japanese buyers—and a shade bitterer, though that oceanic bite can be a good counterbalance to all that lime, cilantro, and onion. An urchin tostada at Pasiano's stand sells for the equivalent of $2; an urchin cocktail with shrimp, octopus, and sea snail goes for $10 to $12. On a good day, he'll make maybe $100.

Even still, Paisano is as much of an institution now as he was in his glory days—royalty deposed and happier for it. Fishermen and tourists and locals stop by to hear his story and to taste the simple fisherman's fare he ate in the days before he struck it rich in the urchin gold rush, before the urchin started to disappear. The assistants who help run the stand, guys like Pancho, are usually former users whom Paisano has decided to mentor, the butt of his bawdy jokes and beneficiaries of his goodwill. His kids are grown up and successful; he and his ex-wife are on good terms. He seems happy—and why not? He has his health and his Bible and his urchin stand, which he named El Pizón for the first of the four rivers flowing into Eden.

As I dug to the bottom of my cocktail for a last chewy morsel of octopus, coated in an orange slick of sweet, briny urchin, Pasiano asked if I knew Genesis 2:10. I didn't, but I looked it up when I got home. The chapter begins with God's first day of rest after the labor of building the world. It describes the tree of life and the tree of the knowledge of good and evil. And then it describes the geography of paradise:

"A river went out of Eden to water the garden, and from there it parted and became four river heads," it reads. "The name of the first is Pizón; it is the one which skirts the whole land of Havilah, where there is gold. And the gold of that land is good."