(Positive) Rheotaxis is a form of taxis seen in many aquatic organisms,[1] e.g., fish, whereby they will (generally) turn to face into an oncoming current.
[5] In fish, the lateral line system is used to determine changes in the oncoming flow pattern of a body of water, and the corresponding orientation of the animal toward or away from the current.
[6] The lateral line sensory system consists of mechanosensory hair cells that detect the movement of water.
For example, sea lamprey will use the flow of the current to identify upstream chemical stimuli, and position themselves towards the direction of the signal.
Recently, it was observed that certain self-propelled particles (gold-platinum nanorods) will rheotax and reorient themselves against the flow in small microfluidic channels.