northern and southern hot springs were re-channeled and merged. The resulting swifter currents caused downstream water temperatures to rise above a level to which the pupfish were adapted. Modifications also allowed the related Amargosa River pupfish (C. n. amargosae) to migrate upstream from the Amargosa River and hybridize with the Tecopa pupfish. In 1966, Miller found that the population at Tecopa Hot Springs was nearly extinct. A population was found at a reservoir at a nearby motel two years later, but its smaller scales suggested that it may have already hybridized with the Amargosa River pupfish. In 1970, concerns over this habitat alteration and the presence of non-native species such as the bluegill and the western mosquitofish led to its inclusion in both Federal and California lists of endangered species. The last confirmed specimens of C. n. calidae were collected on February 2, 1970, and the subspecies was probably extinct by the next year. Further surveys in 1972 and 1977 returned no examples of the fish. In 1978, United States Fish and Wildlife Service announced that it was considering delisting the fish, with Assistant Secretary of the Interior Robert L. Herbst calling the loss "totally avoidable" and saying, "The human projects which so disrupted its habitat, if carefully planned, could have ensured its survival." In 1981, after an exhaustive search of over 40 locations, the Fish and Wildlife Service officially declared the fish extinct. It was the first animal removed from the provisions of the 1973 Endangered Species Act as a result of its extinction. References Cyprinodon Pupfish, Tecopa Pupfish, Tecopa Pupfish, Tecopa Pupfish, Tecopa Amargosa Desert Desert National Wildlife Refuge Complex Natural history of Inyo County, California Taxa named by Robert Rush Miller Fish described in 1948 Fish of North America becoming extinct since 1500 Extinct animals of the United States Species made extinct by human activities Subspecies