From the Super Mario Wiki
Gleamin' Breams are bulky yellow fish from Donkey Kong Country 3: Dixie Kong's Double Trouble! They only in one level, Floodlit Fish. Unlike their red lookalikes, named Bounty Basses, Gleamin' Breams do not have an item contained within themselves, and they cannot be defeated. Gleamin' Breams have a unique ability of being bioluminescent, which means they can produce and emit light.
If Enguarde stabs a Gleamin' Bream with his bill, the Gleamin' Bream makes a shocked face and illuminates the area. After a while, the light fades, so Enguarde must stab the nearest Gleamin' Bream to restore the light. Even though Gleamin' Breams are enemies and are still able to injure the Kongs or Enguarde, they act more like allies because Enguarde is required to hit them to navigate through Floodflit Fish.
Gleamin' Breams appear to be the inspiration for a species of bioluminescent fish in the Donkey Kong Country: Tropical Freeze level, Amiss Abyss. They are small and encountered in schools. Scattering a school of such fish with a corkscrew move makes them produce light for a short time and illuminate the dark area of the stage.
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