After sailing far and wide, Odysseus makes it back home, reclaims his throne, and reunites with Penelope to restore peace to Ithaca. Now, imagine if Odysseus was a salmon. The end of his hero’s journey would not end so gloriously. He would have fertilized some eggs, but not have had the strength to do much else. All of the fat in his flesh that he had accumulated as an adolescent would have burned up during reproduction and his pilgrimage back home. So, his skin starts to rot. His internal organs decompose. His brain works alright, but he would not be able to lift a single bone in his body to fend off the young, lively, virile suitors taking over Ithaca. All he could have done is linger and float in the water, half-dead.
Salmon famously return to their birthplace after their great migration around the entire ocean. They make it back to their exact spawn location to lay or fertilize their eggs, but these environments have nowhere near enough life to sustain the feasts that salmon are used to in the open seas. Once their body fat has been completely consumed through exerting energy for spawning, their muscles degenerate. Furthermore, their intestines atrophy, hindering absorption of nutrients. High levels of plasma cortisols degenerate tissues and compromise their immune systems. To complicate matters, skeletal needles begin to replace and deform the salmon’s upper jaw, forming a hook called a kype that makes it difficult for them to completely close their mouth. Although uncertain, it is the consensus for now that the development of this curved jaw is used by males to attract female salmon by fighting each other, as impractical as it may be for catching prey. In addition, the kype develops at a cost. The bones for the replacement jaw need calcium to grow. Without many natural sources of calcium in the spawning environment, the salmon reabsorb their silvery scales and reveal the inflamed shade of flesh that lies underneath. This is what gives the spawning salmon their iconic scarlet color. As the salmon continue to live in this accursed state, their flesh starts rotting and their eyeballs pepper the riverbed as treats for scavengers. Mind you, they are still conscious. They give off the appearance of a corpse, hence the name “zombie salmon.” Although these are still safe to consume, it can often be difficult to differentiate between a live zombie salmon and a rotting cadaver of a salmon.
The bodies then accumulate in streams, forming graveyards as trees and roots snag them. They enrich the body of water and become feed for insect larvae and nutrients for algae. The life that develops from the death of salmon then becomes the main source of food for adolescent salmon hatching from their spawn, fueling their bodies as they prepare to embark on the same journey as their parents. The cycle then continues again and again.
There is nothing to fear from zombie salmon, as it is because of the mere appearance of their decomposition that humans gave them the name. The “zombification” of salmon acts more as paralysis, with salmon being rendered immobile as they near the end of their life cycle. Their bodies do decompose like the typical zombies seen in movie franchises, zombie salmon are not reanimated, nor contagious, and their minds act more similarly to the minds of the infected in the 28 Days Later franchise. Even though the name given to the process might seem scary (and it does appear disgusting), it is simply the stage of degeneration of a salmon’s body while they live on and slowly reunite with nature.