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Magnetic Crystals in Salmon Help Them Return to Their Home Streams

Like butterflies and birds, salmon migrate using earth's magnetic field. Scientists think animals evolved natural compasses from bacteria.

by | February 18, 2022

Like most species of salmon, sockeye spend their adult lives at sea. Salmon migrate back to their original lakes and streams using the earth's magnetic field.
Like most species of salmon, sockeye spend their adult lives at sea. Salmon migrate back to their original lakes and streams using the earth’s magnetic field.

Every year, juvenile salmon smolts leave the lakes and streams of their birth for the open sea. Meanwhile, adult salmon return home to those exact same lakes and streams. How do salmon, and other animals, navigate thousands of miles with such precision? Researchers at Oregon State University have discovered a connection between the built-in compass of magnetic crystals in salmon noses.

What Is Magnetite?

Magnetite is a strongly magnetic iron ore. Most iron mines extract magnetite, which factories process into pure iron and steel. Likewise, animals have natural deposits of magnetite — from bacteria to human beings. Scientists believe that migratory bats, birds, and butterflies can detect the Earth’s magnetic field using magnetite in their bodies. They also believe magnetite is what helps young ocean-bound salmon return to their spawning grounds.

Why do our bodies contain magnetite? Scientists theorize that magnetite navigation systems may have developed in bacteria two billion years ago. As these microbes evolved into more complex organisms, the magnetite remained.

But if magnetite helps animals migrate, where can scientists find it in their bodies? At least in salmon, researchers believe they may have the answer.

Magnetite in Salmon Noses

In a paper published in Proceedings of the National Academy of Sciences, fisheries scientist Renee Bellinger reports magnetic material in the noses of salmon. The magnetite particles were so small and scarce, they’re very hard to detect. However, Bellinger’s research could lead the way to making these cells “glow really bright so we can find and understand receptor cells more easily.” 

Bellinger began her research as a doctoral student at Oregon State University. She is now a research geneticist with the U.S. Geological Survey and affiliated with the University of Hawai’i, Hilo. 

Twenty years ago, another study in New Zealand looked at magnetite in the noses of trout. In that study, researchers traced the magnetite to the olfactory rosette. This fan-shaped structure relays smells and other sensory information to the brain. The magnetite crystals found in salmon were similar to those found in bacteria. Single-cell organisms grow the crystals into needle shapes that work like magnetic compasses.

Applying the Research

Her co-author, Michael Banks, a professor of Oregon State University fisheries genomics, conservation and behavior, says the study could help salmon managers better understand how salmon behave in the open seas.

[Salmon] don’t have the opportunity to teach their offspring where to go, yet the offspring still somehow know where to go. If we can figure out the way animals such as salmon sense and orient, there’s a lot of potential applications for helping to preserve the species, but also for human applications such as medicine or other orientation technology.

Dr. Michael Banks, Oregon State University fisheries science professor 

The project also included researchers from China, France, and Germany. Next, the team will test their new understanding of how magnetite helps salmon migrate to unravel the mystery of why certain migratory animals can return home with such precision. 

How CIAA Uses Salmon Migration to Enhance Fisheries

The Cook Inlet Aquaculture Association uses this remarkable migratory instinct in salmon to produce more abundant returns in certain streams throughout the Cook Inlet area. CIAA catches adult salmon to be used as broodstock, hatching their fertilized eggs, and releasing smolts into designated streams. Years later, those fish return to the area they were released to provide a common property harvest for fishermen and help hatcheries with cost recovery.

See What’s Hatching at CIAA

To see how Cook Inlet Aquaculture Association is involved with the early lifecycle of salmon, schedule a tour of one of CIAA’s hatcheries.

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