A team of international researchers led by Northwestern University has concluded a study that discovered why Zebrafish look down while swimming forward.
The team found fish need to look down when moving forward to stay stable. The adaptive behavior evolved to help the fish self-stabilize in moving water.
By looking down, the fish can pick a specific physical spot that will not move and maintain its orientation to it. This is far more reliable than trying to use another fish or seaweed as a reference point since these are likely to move, resulting in confusion and a loss of orientation.
Commenting on the finding, Emma Alexander, the study lead and assistant professor of computer science at Northwestern’s McCormick School of Engineering, stated:
“It’s similar to sitting on a train car that isn’t moving. If the train next to yours starts to pull to away from the station, it can trick you into thinking you are moving too…The visual cue from the other train is so strong that it overrides the fact that all of your other senses are telling you that you are sitting still. That’s exactly the same phenomenon that we are studying in fish. There are many misleading motion cues above them, but the most abundant and reliable signals are from the bottom of the river.”
“We tied everything together into a simulation that showed that, in fact, this is an adaptive behavior. The water surface is constantly moving, and other fish and plants are moving by. Fish are better off omitting that information and focusing on the information below them. Riverbeds have a lot of texture, so fish are seeing strong features they can track.”
You can find the original study here.