Science question: How do scientists test the idea that trout could migrate using the magnetic field?

In the spring when water temperatures start to rise, rainbow trout that have spent several years at sea traveling hundreds of miles from home manage, without maps or GPS, to find their way back to the rivers and streams where they were born for spawning. Researchers have identified genes that enable the fish to perform this extraordinary homing feat with help from Earth's magnetic field.

Explanation:

the answer would be 32*f