BASS (Morone labrax), a fish of the sea-perch family (Ser ranidae) found in the Mediter ranean and on the Atlantic coasts of Europe. It is a silvery, blue backed fish, with a strong spi nous dorsal fin ; it grows to 3 f t. in length. Bass swim in shoals near the coasts and often ascend rivers. There are four American species of Morone, and the name THE SMALL-MOUTHED BLACK BASS bass is also given in America to (MICROPTERUS DOLOMIEU) other sea-perches, as well as to the black bass (Micropterus) and other highly prized fresh-water game fishes of the family Centrarchidae.