(FORTUNE Magazine) – THE CARPET OF SUSHI-GRADE TUNA lining the floor of Tokyo's Tsukiji fish market offers a tempting display of the day's catch for wholesalers willing to bid tens of thousands of dollars for a specimen. On this particular morning in January one dealer paid $35,000 for a single 455-pound tuna. The splurge is not surprising in a country whose voracious appetite for the fish makes it the world's biggest tuna consumer. That same sight, however, troubles marine biologists and experts, who say that as worldwide demand for sushi, as well as for canned tuna, has increased, the ocean's fish population has been dramatically depleted. Technological advancements in recent decades, from sonar to high-grade netting, have made fishing more efficient. According to one UN study, the amount of tuna caught around the globe today is ten times what it was in 1950. "It's the equivalent of everybody running to the same tree with a chainsaw," says Katherine Short, a fisheries expert at the World Wildlife Fund. In late January the world's five regional fisheries-management organizations set up to regulate tuna fishing in international waters met for the first time in Kobe, Japan. The groups agreed to develop a unified catch-tracking system, which may require tagging legally caught fish to prevent poached ones from entering the market. And they agreed to share lists of illegal fishing fleets. But the regional organizations failed to set any catch quotas or even a timeline for doing so. In the meantime, the demand for tuna is likely to increase, and at fish markets like Tokyo's Tsukiji the selection may dwindle and the prices rise even higher