Science: The Pied Piper of Hamburg

An unsportsmanlike plot, involving a low trick on fish, is being cooked up by Dr. Konrad Kreutzer, a well-known German physicist. According to an official report last week in the U.S. Department of Commerce’s Foreign Commerce Weekly, Dr. Kreutzer put two electrodes in the water of Lake Constance, passed a current between them, and observed (as had been observed before) that fish in such a spot tend to head toward the positive electrode. He also observed that an increase in the current made their tails wiggle. This gave him his big idea. When a fish’s tail wiggles back & forth, the fish is swimming. Why not force him, by electricity, to wiggle into a net?

The big job was to find just how to vary the current. To make the fish wiggle properly, he discovered, the intensity of the current must rise suddenly and die away slowly. Such “pulses” must be about two-thousandths of a second long. The pause between pulses must be timed to the natural swimming motions of the fish. Since little fish move their tails faster than big fish, the pulses must come closer together (about 20 per second) to catch little fish. A current with two pulses per second catches big ones.

When his apparatus is working right, Dr. Kreutzer claims that fish swim to their deaths as if bewitched. The Herr Doktor turns on the current; the fish point dutifully toward the electrode. When he makes the current sing its pied-piper song, the fish wiggle and waggle in time with the subtle pulses. Glassy-eyed and helpless, they swim toward the electrode which leads to the frying pan.

Dr. Kreutzer has demonstrated his electronic fish-catcher at Hamburg, and has convinced many commercial fishermen that it will revolutionize their business. One practical way to use it would be to draw fish into the path of a towed net.

Properly timed, thinks Dr. Kreutzer, the singing current would even catch whales, forcing them to swim right up to the maw of a whale ship. When the whales arrived, he suggests, the current could be intensified, stunning them temporarily. Then the whalers or whale inspectors could measure each leviathan, noting its sex and its depth of blubber. Large, fat males could be hauled aboard. The young, the thin and the female could be set free with the crew’s apologies.