Blenny is a common name for many types of fish, including several families of percomorph marine, brackish, and some freshwater fish sharing similar morphology and behaviour. Blennies are mostly small, usually marine fishes found from tropical to cold seas. They are slim, ranging in form from moderately elongated, as in some of the tropical species, to very long and eel-like, as in the gunnel and wolffish of northern waters. As a group, however, they are united by such features as a long dorsal fin and pelvic fins, when present, that are placed near the throat and contain one spine and two to four rays.