Ask a Naturalist: How do salmon know how to return to their birthplace?
October 27, 2020
Written by Sara Tabatabai
Salmon are known for their incredible migration patterns! Born in the river, they travel to the open waters of the ocean where they live for up to seven years before returning to their birthplace for spawning. The purpose of returning to the exact place of their birth is that it offers salmon a higher chance of successful reproduction because it is a familiar area proven to be perfect for spawning. Traveling to a random river comes with uncertainties: the river may not have mates of the same species or conditions may not be favorable for certain types of salmon.
So how do they find their way back home?
There are two main, likely theories as to how: use of the Earthís magnetic field and their sense of smell.
Recent studies have shown that while in the vast and open ocean habitat, salmon use the Earthís magnetic field to guide their migration. Fish use this system the same way humans use GPS - it allows them to figure out their location and directs them to their destination. Unlike using scent as a navigational tool, utilizing the Earthís magnetic field is most likely genetically inherited rather than learned during migration.
Salmon have a keen sense of smell (better than humans) that help them detect and avoid predators, find food, and attract a mate. Since birth, salmon imprint on (or learn) the smells unique to their spawning site. As they travel downstream towards the ocean, itís highly possible that they memorize particular scents at various points along the way. Once they reach adulthood and are ready to reproduce, they can pick up on those familiar scents that help them navigate back home.
Other theories include the use of other environmental clues such as the sunís position, and water salinity and temperature gradients. Itís likely that salmon use a combination of these navigational tools to direct them to where theyíre meant to go!
Learn more about the Salmonís incredible migration by checking out this video (or click the image below) by National Geographic!
Also watch this outstanding National Geographic Wild video showing the arduous challenge salmon face when swimming upstream (or click the image below)!
Using toilet paper rolls, paper, string, and a stick, create these really adorable fish inspired by Koinobori (Japanese flying carp streamers)!
Dive more into the world of salmon by downloading and printing this free Salmon Activity Book from Columbia River Inter-Tribal Fish Commission!