Brood stock of critically endangered bonytailGila eleganswas obtained between 1976 and 1981 from Lake Mohave, Arizona-Nevada, and propagated by artificial means and by natural reproduction in ponds at Dexter National Fish Hatchery, New Mexico. Twenty-four naturally produced F2individuals were examined electrophoretically for soluble gene products of 45 loci. Six polymorphic loci were identified: aspartate aminotransferase (sAat-A), glucose-6-phosphate isomerase (Gpi-B), and phosphoglucomutase (Pgm-A) from skeletal muscle; esterase (Est-2) from brain; and catalase (Cat-1) and L-iditol dehydrogenase (Iddh-A) from liver. Electromorph distributions at each locus agreed with Hardy–Weinberg expectations. Hatchery bonytail had a lower mean level of heterozygosity than arroyo chubG. orcutti. However, direct-count heterozygosity for bonytail was comparable to mean values reported for other western North American cyprinids. Allozyme variation expressed by hatchery-produced bonytails suggested a genetically variable stock suitable for reintroductions into appropriate wild habitats.