Magazine article Science News

Catfish Can Track Fish Wakes in the Dark

Magazine article Science News

Catfish Can Track Fish Wakes in the Dark

Article excerpt

Infrared photography has revealed that European catfish can stalk prey by tracking underwater wakes much as hunters on land follow footprints.

This laboratory demonstration marks the first time that scientists have described a fish following another fish's wake in the dark, according to project leader Thomas Breithaupt of the University of Konstanz in Germany. Catfish pick up a trail 10 seconds after a guppy waggles by and pursue that trail for up to 55 guppy body-lengths before striking, Breithaupt and his colleagues reported June 5 in the online PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES.

"It's a fascinating paper. I loved it," comments Jeannette Yen of Georgia Institute of Technology in Atlanta. In 1998, her research team made the first detailed report of any underwater wake tracking. Yen found that male copepods, pinhead-size marine crustaceans with only primitive light sensors, chug along the tiny wakes left by females. As it turns out, males often start off in the wrong direction and have to turn around.

For years, Breithaupt has wondered whether fish hunting in the dark follow wakes, but only recently did he find a convenient species to test. The European catfish, Silurus glanis, prowls by night. Examination of its stomach contents indicates that it often manages to catch swift prey.

Breithaupt, his Konstanz colleague Kirsten Pohlmann, and Frank Grasso of the Boston University Marine Program in Woods Hole, Mass., set up an infrared fish-monitoring system in a large laboratory tank. The researchers then placed a 20-centimeter-long European catfish into the tank and added a guppy. They next recorded and statistically compared the pathways that the two fish plied in the dark.

Sometimes the fish merely blundered into each other. But nearly 60 out of 90 catfish attacks on the guppy came after the catfish had twisted and wriggled along the same meandering path that the guppy had just taken. …

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