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Zombie salmon: The plight of the swimming dead 

After they reproduce, salmon eventually die — but not right away. For a few weeks, zombie salmon keep swimming as they literally fall apart.

by | October 27, 2022

Not dead yet, and not quite alive, zombie salmon can be a scary sight! Trenton Schipper, CIAA

Their skin is pallid gray, covered with mold, and beginning to fall off. Their heads are sometimes bumpy and squishy. They may be missing an eye or two. Yes, zombie salmon are real — sort of. Unlike movie zombies, they’re still alive, barely, and they don’t eat anyone’s brains. Zombie salmon are fish that have returned to their freshwater spawning grounds but are still in the twilight zone between life and death.

They might be creepy and gross, but zombie salmon help feed the plants and animals around them as they decay. 

After salmon spawn, they lose their bright colors. It takes a few more weeks before the fish are dead. CIAA

When the life cycle is over

After juvenile salmon leave their natal lakes and streams for a life at sea, their magnetic sense of direction leads them back. These adults swim upstream to reproduce, a process called spawning. Once they have released and fertilized their eggs, it only takes a few weeks for those salmon to die.

During those weeks, those fish become shadows of their former selves. Their bodies begin to shut down and actually rot. Hearts, arteries, and muscles fall apart. Digestive organs shrivel up. The skin loses its bright, colorful hues. 

CIAA biologist Emily Heale gets up close and personal with a zombie salmon. You may want to think twice before making a meal of one. CIAA

Can you eat a zombie salmon?

If you eat a zombie salmon, you won’t turn into a zombie yourself. You just might not find it very tasty. You know that fat that makes salmon so delicious? It was burned as energy during the fish’s long journey home. 

Also, there’s a fine line between a zombie salmon and a dead salmon, which can make you sick. Dead fish will have a higher amount of dangerous bacteria than those still alive with healthy immune systems. 

What good are zombie salmon?

The best thing about zombie salmon is that they very quickly become dead salmon. Those corpses feed birds, which especially like to feast on the eyeballs. Flies and other insects lay their eggs in the rotting carcasses – the same flies that will feed the baby salmon that will hatch from eggs in nearby gravel beds. As they continue to decay, dead salmon washed up on shorelines and river banks fertilize trees and other plants.

The rest of the life cycle

Are you curious about how salmon are born, live, and die? The Cook Inlet Aquaculture has put together a colorful chart explaining the stages of a salmon’s life cycle.

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The Cook Inlet Regional Planning Team meeting is set for December 13, 2022 at CIAA. Contact CIAA for more information.
The Cook Inlet Regional Planning Team meeting is set for December 13, 2022 at CIAA. Contact CIAA for more information.