the gill operculum covers and protects the gills.
That is a hard but flexible cover which, in bony fish, forms the outer wall of the gill chamber. It protects the gills and also plays a major role in the pumping mechanism that regulates the continuous flow of water over them.
don't you mean: what does the gill arch do in a fish?!
The gill rakers on fish keep food particles from moving out from in between the gill arches. For filter feeding fish and some suspension feeding fish, the gill rakers function is to trap the food.
It is used to cover the gill on the fish.
a gill cover is used to cover the gill on the fish
gill is a part of a fish.
The flap of tissue that covers a bony fish gill is the bony operculum.
gill slits
Gill.
A fish breathes through its gills.
gill slits
The black and white fish Named "Gill" from Disney/Pixar's Finding Nemo is a Moorish Idol. Though aquariums often state this fish as a Black and White Heniochas.