Sense
Magnetoception (or magnetoreception) is the ability to detect the direction one is facing based on the Earth's magnetic field. Directional awareness is most commonly observed in birds, which rely on their magnetic sense to navigate during migration. It has also been observed in insects such as bees. Cattle make use of magnetoception to align themselves in a north-south direction. Magnetotactic bacteria build miniature magnets inside themselves and use them to determine their orientation relative to the Earth's magnetic field.
Magnetoreception
Studies of magnetoreception in vertebrate fish have been conducted mainly with salmon. For instance, the presence of an internal magnetic compass has been discovered in Sockeye Salmon ("Oncorhynchus nerka"). Researchers made this discovery by first placing the young of this species in a symmetrical, circular tank and allowing them to pass through exits in the tank freely. A mean vector was then calculated to represent the directional preferences of these salmon in the natural magnetic field. Notably, when the magnetic field was experimentally rotated, the directional preferences of the young Sockeye Salmon changed accordingly. As such, researchers concluded that the orientation of swimming behaviour in Sockeye Salmon is influenced by magnetic field information.