快猫短视频

CATFISH in pursuit of a tasty meal could teach robotic lobsters a thing or
two about finding their prey.

Just like boats or aircraft, fish on the move create a three-dimensional wake
made up of swirling eddies, or vortices, leaving a residual disturbance that can
last more than five minutes in still water. Kirsten Pohlmann and Thomas
Breithaupt of the University of Konstanz in Germany wondered if predatory fish
like catfish could use the motion of these eddies to track their prey.

Like other fish, catfish have small pressure-sensitive organs on their head
and along their sides that enable them to detect even tiny water currents.
Marine biologists had thought these helped fish to swim and to synchronise their
movements in larger schools.

But Breithaupt鈥檚 group has discovered they have another use. In tests in the
dark, they found that catfish in hot pursuit of a guppy didn鈥檛 go directly for
them. Instead, they followed the prey鈥檚 wake precisely, sometimes moving from
side to side, checking out the edges of the eddies.

The wake of a fish includes primary eddies set up by the passage of the body
and secondary eddies set up by the motion of the tail. 鈥淭hey could use the
direction of these eddies to tell which way the wake points,鈥� Breithaupt says.
He suspects further tests will show that sharks, eels and other predatory fish
use the same trick. 鈥淭his will be very important at night, in the deep sea or
turbid water,鈥� he says. 鈥淧rey can swim but they can鈥檛 hide.鈥�

Now Breithaupt and Pohlmann鈥檚 colleague Frank Grasso, a roboticist at Boston
University, is interested in applying the discovery to the design of his
鈥渞obotic lobster鈥濃�攁 chemical-sensing aquatic robot with wheels that
scuttles around on the bottom of a tank. The lobster currently follows a plume
of chemicals underwater by measuring changes in concentration, but Grasso says
he now wants to give it motion sensors too.

鈥淭hey may not need a full-blown model of wakes but we could program them to
use particular features like the vorticity,鈥� he says. Grasso is especially
interested in the way that wake patterns and chemical traces from moving fish
interact, with the traces becoming trapped in the swirling eddies.

Breithaupt thinks one application of such systems, whether in a robot or a
stationary sensor, could be for fisheries inspectors or marine biologists who
are trying to keep tabs on fish. 鈥淲hen fish swim they don鈥檛 produce a sound, so
it鈥檚 not easy to track them,鈥� he explains.