The Chemistry of Salmon


  • Salmon are a member of the Salmonidae family. They are anadromous, so they are born in freshwater, migrate to saltwater, then return to the fresh to reproduce. They are generally divided between Pacific and Atlantic salmon. As an avid fisherman, I find the habits of salmon interesting and decided that this project would be a great way to figure out the chemistry behind their actions and share with everybody!Composition of ...
    • Body
      • Head
      • Fins
        • Dorsal
        • Pectoral
        • Adipose
        • Anal
        • Pelvic
      • Tail
      • Gills
    • Brain
      • Iron
    • Muscles
      • White muscles
        • Used for bursts of energy, explosive power (jumping, surging, fighting, ect…)
      • Red muscles
        • Used for long periods of sustained swimming (oceanic travel)
    • Nose
      • extremely sensitive olfactory glands

Main Chemicals, Compounds, Components

How do salmon find their natal stream? Iron is present in salmon brains. Scientists speculate that this may allow the salmon to be magetaconceptic. This means they can detect slight variations in the Earth’s magnetic field, allowing them to navigate in open ocean and find their way back to their natal stream. Since salmon die after spawning, newborn salmon inherit this information, it is not learned. Research has shown that even salmon who were born in captivity responded accordingly to simulated magnetic fields. Once a salmon has found the river it was born in, its navigation is driven mainly by olfactory glands (smell) because not only do salmon find the exact river they were born in, but often the very gravel bed. They do this by honing in on trace elements and, as recent studies suggest, certain amino acids.

At the end of the salmon spawn, all of the fish die (Pacific), but they have just started to give back to the ecosystem. N-15, a heavy and rich, but rare, isotope of nitrogen, grows abundantly in marine algae. As a result, salmon are rich in N-15. The annual salmon run brings a large influx of N-15 into ecosystems that would otherwise have little to none. This brings up an interesting relationship between salmon and bears. Bears migrate from miles around during the salmon run to gorge on these vulnerable fish. One study suggests that an individual bear will capture up to 700 pounds of salmon in one run and that only half of each salmon is consumed by the bear. The rest is scavenged and decomposed. Bears bring the N-15 rich salmon carcasses as far as 1000 meters from the water source, effectively distributing the N-15.

Chemistry's Role

    • Iron in the brain-magnetic navigation
    • Chemical cues trigger physiological changes
    • Extremely strong sense of smell identifies trace elements (imprinting)
  • Nitrogen-15: rare stable isotope of nitrogen that is extremely fertile for plant growth.

Background Research

Salmon are a member of the Salmonidae family. They are anadromous, so they are born in freshwater, migrate to saltwater, then return to the fresh to reproduce. They are generally divided between Pacific and Atlantic salmon. A salmon is born in a freshwater river. It then migrates to the sea where it lives for several years before it is fully matured. When a salmon reaches full maturity, it will begin its spawning run along with thousands of other salmon. Salmon come from thousands of miles and are able to find their exact natal river. As they enter fresh water their body compositions undergo several drastic changes. Their stomachs begin to dissolve to make room for their sexual organs. Males may develop a shoulder hump, canine teeth and a kype (hooked jaw for fighting.) Their red muscles deteriorate while their white muscles grow stronger. They return to the place of their birth to spawn. After spawning, most Atlantic salmon and all Pacific salmon die. The death of these thousands of salmon is vital for the local ecosystems around the rivers they spawn in. All of these dead salmon return vital nutrients to the earth including nitrogen. phosphorus and sulfur, not to mention the wildlife that gorges on these easy meals every year. The newborn salmon, called fry, will live in the river until they are juveniles. They then migrate to the sea to restart the cycle.


Pacific vs. Atlantic species, life cycles, diet

Spawning habits of salmon. Pacific species die after spawning, Atlantic may spawn up to 5 times.

Lots of information on how a salmon in the ocean finds its natal stream, even its specific birth-place. Also chemical triggers from fresh water and their effects on the salmon’s body.

Awesome! Actual experiment comparing higher river temperatures as a result of climate change to the mortality rate of spawning sockeye salmon.

In depth analysis of how salmon use magnetic navigation to find their natal streams.

This is an analysis of the biological and chemical effect salmon migrations have on inland ecosystems (predators, returning nutrients to the earth ect…)

Study of how salmon use Earth’s magnetic field to navigate in the ocean.

Describes olfactory navigation in fresh water.

About the Author

Connor Maas is a junior at Billings Senior High School. For sports he is the captain of the swim team. He also enjoys the many outdoor opportunities that Montana has to offer, including fly fishing and photography. After high school he plans to attend Montana State University and continue his outdoor expeditions and pursue a career in photography.