Any of a few hundred species of egg-laying topminnows (seeguppy) in the family Cyprinodontidae. They are found worldwide in brackish, salt, and fresh water, including desert hot springs. Some species grow to 6 in. (15 cm) long. Killifish eat plant or animal material at the water's surface. Many species (e.g., the lyretail) are attractively coloured and are kept in home aquariums. Killifish are also valuable as bait and for mosquito control. Pupfish (Cyprinodon) inhabit California coasts and certain salt-lake shores in the western U.S. Some pupfish are listed as endangered; the Tecopa pupfish (C. nevadensis; 0.6 in. [1.5 cm] long) was declared extinct in 1981.