What is the function of gill rakers of a perch? and another fish question.

Question

1.I know that they help filter feeders retain organisms, but I don't think perches are filter feeders though

2. What is the advantage of having luminescent or glow in the dark skin?

Answer 1

Gill rakers increase the surface area of the gills.  The more surface area of the gills are in contact with water, the more oxygen they can pull out of the water.

Luminescence can attract prey, or members of one's own species.