Salmon Homing Mechanism

According to Eugene M. McCarthy, the bright fish have the ability to sense the earth's magnetic field. When they are young, the salmon imprint on the magnetic filed to where they were born and when they mature they use the magnetic field as a guide to find the location of their home. It has also been thought that other sea animals such as seals and sea turtles use the earth's magnetic field as a guide as well.

A study on the salmon in British Columbia's Fraser River Watershed by Nathan Putman helped clear up if salmon do indeed sense the magnetic field. They choose this area because it is one of the most important salmon-producing regions in the world. When designing the study, Putman and his team guessed that if the salmon did follow the magnetic fields, their behavior and where they went would be predicatable. The guessed this because the earth's magnetic field changed gradually over time. The salmon movements and megnaetic field chnages over the last 58 years were known whcih gave them an idea of where the salmon would go.

After the study, it was concluded that the salmon took the passage that went around Vancouver Island. This matches the magnetic field value of the Fraser River, which was when they first emerged into the ocean. This and other compared data indicates that salmon do indeed sense the magnetic field as a homing device. 

Nature of Science Themes:
Science is based on evidence: Nathan Putman observed the samlon and discovered the salmon did follow a magnetic field guide
Science is repeatable: The salmon always return to where they were born which is why there are always so many salmon going to a certain area
The role of motivation and curiosity: A person was interested and curious about how salmon know how to swim home, so they conducted an observation to see why the know the way

http://www.macroevolution.net/salmon-homing-behavior.html
http://www.cell.com/current-biology/abstract/S0960-9822(13)00003-1