|This article is about a/an kaijin in Kamen Rider Black.|
When the Misuzu River was working in reverse as part of Gorgom's latest plot to drain it of its water, Bilgenia unleashed toxic waste from the oil refinery at Tokyo Bay and sent it to Red Salmon Mutant. Kohtaro encountered a paraplegic boy named Toru who saw Red Salmon Mutant. Darom also mentioned that Red Salmon Mutant had a lot of training all over the world which one of them was causing ships to disappear in the Bermuda Triangle. Red Salmon Mutant attacked when Kohtaro encountered Toru near the river. Kohtaro transformed into Kamen Rider Black and fought Red Salmon Mutant. Red Salmon Mutant made off with Toru with Kamen Rider Black in pursuit. Red Salmon Mutant knocked Kamen Rider Black into an underground cavern that was recently expelled of its water. With Toru strapped to the wall, the Gorgom High Priests unleashed Red Salmon Mutant upon Kamen Rider Black. When Red Salmon Mutant had Kamen Rider Black trapped in his jaws, Kamen Rider Black called for Road Sector who tackled Red Salmon Mutant, smoked out the Gorgom High Priests, and freed Toru. Kamen Rider Black managed to lure Red Salmon Mutant out of the underground cavern. As Toru escaped on Road Sector during the battle, Darom attacked him and flung him onto the suspension bridge. Red Salmon Mutant spewed red substance on Kamen Rider Black until he used the Kingstone Flash to get it off and repel it onto Red Salmon Mutant. Once Kamen Rider Black killed Red Salmon Mutant with the Rider Kick, its effects on the Misuzu River were undone.
It can bite, manipulate water, and spew red substances from its salmon-headed hands.