January 19, 2006—Pitting two hands against thousands of stinging tentacles, a diver attaches a tracking device to a giant Nomura's jellyfish off the coast of Japan on October 4, 2005.

Since last summer, Japanese waters have been inundated with the massive sea creatures, which can grow 6.5 feet (2 meters) wide and weigh up to 450 pounds (220 kilograms).

Though the jellyfish are more common in Chinese and Korean waters, their numbers have grown a hundredfold in some areas off Japan, causing a crisis in the local fishing industry.

The invertebrates are choking fishing nets and poisoning the catch with their toxic stingers, fishers say. And although reports of serious human injury are rare, there are records of people dying from the creature's noxious sting.

The invasion has prompted a series of studies by the Japanese government to research the animal, whose mating and migration habits are poorly understood.

Last month, Japanese scientists speculated that the jellyfish are drifting from China's Yangtze River Delta, where unusually heavy rains may have created a flow that is pushing the jellyfish flotilla to Japan.

Another theory suggests that seas heated by global warming are better suited for breeding, turning the Nomura's otherwise modest numbers into an armada.

As the research continues, Japanese fishers continue to grapple with another issue: What to do with all the jellyfish they've caught? So far, resourceful anglers have turned their unwanted catch into crab food, fertilizer, and novelty snacks—served dried and salted.

—Blake de Pastino, National Geographic Society