Every day for 16 years, researchers watched a tank of catfish to see if the fish lived up to their fabled prowess at forecasting earthquakes.
The fish acquitted themselves well, but not reliably enough to please the precise demands of science. So, the city has sent the fish into retirement.
The money for the project--some $60,000 in 1991--will be used to fish for other ways to predict quakes.
Tokyo sits near several geological faults, and 140,000 people died in a 1923 earthquake and resulting fires.
City officials say another major earthquake could hit soon. They predict that it could kill at least 10,000 people and injure 150,000.
Yasuo Baba of the Tokyo Metropolitan Marine Experiment Station said researchers studied old books and folk tales and discovered frequent accounts of links between catfish and earthquakes.
"In Japan, there is a widespread belief that catfish become more active before earthquakes, so we decided to see if it's true," he said.
Electronic sensors monitored the fish 24 hours a day and relayed information about their movements to a computer. The information was compared to records of earthquakes kept by the Central Meteorological Agency.
Consistently, all seven of the usually sluggish fish greatly increased their activity several days before about 31% of earthquakes that registered "quite strong" or higher on the Japanese earthquake scale, Baba said.
Five or six of the fish perked up before 60% to 70% of the quakes, he said.
"That's better than a random association," Baba said. "We believe the research was successful, but our sponsors in the Tokyo government didn't think it was going anywhere. They want to discover ways to predict a major earthquake, but the fish are sensitive to even shallow ones."
Research now is needed on what kinds of signals are released by impending earthquakes and why catfish apparently are able to sense them, he added.
"If we're able to find that out, we won't need catfish anymore. We can make equipment that can predict earthquakes directly," he said.
Separate research conducted at Tokyo University suggests that catfish may be sensitive to shifts in extremely weak electrical fields that could be caused by earthquakes-in-the-making. That sensitivity, Baba said, could be linked to some kind of sonar-like device used by the weak-eyed fish to locate food.
Japanese catfish belong to different species than the American variety.
"American catfish are not good at earthquake predicting. They're only good for eating," Baba said.
Tokyo's quake forecasters are to be spared that fate.
"They've worked very hard for us, so we're going to give them a well-deserved rest," he said.