Using a new type of laser imaging technique, researchers have been able to show for the first time that the dorsal and anal fins of fish are used for more than just stabilization during swimming. The full results of the study were published in Biology Letters on April 20th.
The new type of imaging technique uses a container equipped to provide constant unidirectional water flow along with tiny plastic beads and short bursts of laser pulses to map in 3 dimensions how these plastic beads flow in the wake of the fish as it maintains its position in the tank. It’s essentially a “a treadmill for fish.”
What they have shown is that both the dorsal and anal fins (the fins on the top and bottom of the fish) are actually used for forward locomotion as opposed to just stabilization of the fish as once thought.
“We knew the dorsal and anal fins are very important for balance, and although a locomotory role was suspected, we have only now been able to show that they also play a big part in locomotion,” Flammang said.
There is a short video on Harvard’s website that shows about 4 seconds of how this technique is employed in measuring the flow around the subject. Unfortunately Harvard’s website doesn’t provide an embeddable video so head over and watch how they accomplished the task.