Mouth - an apparatus used for capturing and holding prey, crushing, filtering and squeezing food. In some species of fish mouth serves to nurture fertilized eggs (many tropical fish) and shelter for fry. Distinguish the mouth grabbing (pike, catfish, pikeperch), in the form of a suction cup (hagfish, lampreys), suction, usually retractable (bream, crucian carp, carp), crushing (catfish), planktonoids (herring, herring), periphytonoids (podust, tempura). Depending on the nature and mode of feeding distinguish three types of mouth: upper, terminal and lower. Sometimes transitional types are distinguished: semi-upper and semi-lower.