There are three types of mouth in fish:

Upper (semi-top) mouth - the lower jaw protrudes upwards (vendace, roach, silver carp)

Terminal mouth - the jaws are the same length (bullhead, omul, mackerel)

Lower (semi-lower) mouth - upper jaw, or rostrum, protrudes strongly forward (cartilaginous fish, sturgeon)

An upper mouth in fish where the lower jaw is longer than the upper jaw and lies above the axis of the body. The mouth opening is directed upwards. Found mainly in planktophagous fish (cichonka, ryapushka) living in the upper horizons; characteristic of ambush predators (sea devil, catfish). Occasionally a half-lipped mouth is noted, as in the bleak.