The creatures have been branded as similar to those in new Harry Potter film Fantastic Beasts and Where to Find ThemCredit: CENRoman, from the city of Murmansk, regularly posts photos online which often cause a stir among his followers.
The pictures feature slimy creatures with bug eyes and razor-sharp teeth.
Some have been been likened to a̳l̳i̳e̳n̳s from another planet.
Some of the hulking beasts are so big, Roman’s nets can barely contain them.
He revealed that his favourite ever mutant fish looks like a prehistoric shark with bizarre teeth.
And the experienced fisherman is often stumped by the species he catches and relies on social media users to help identify them.
One user said: “Those fish are awesome.”
While another added: “I hope I won’t get nightmares after seeing all these beasts.”