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ENDANGERED SPECIES 367 judiciary, Congress, the media, and administrative agencies interact to determine how the ESA, a statute intended to be prohibitive, is implemented. 15.4.3 Death Valley Fishes Another case of vanishing fishes which involved intervention by the Supreme Court is that of the desert fishes of Death Valley. Scientists disagree on historic drainage patterns in the Death Valley region of southwestern Nevada and southeastern California, but they agree that much of the area was covered by large lakes interconnected by rivers during the Pleistocene epoch (Soltz and Naiman 1978). Today, Death Valley is one of the hottest and driest places in the United States, and its waters have largely shrunk to a few small spring pools and intermittent streams. The Owens and Mohave rivers receive runoff from within the basin, but much of the basin's water enters through two groundwater systems, the Pahute Mesa and Ash Meadows groundwater basins. Only a few native fishes existed in Death Valley at the turn of the century. Among them were killifishes (several species of Cyprinodon and two of Empetrichthys), minnows (speckled dace and tui chub), and the Owens sucker (pister 1974, 1981). Many lived in very restricted habitats subject to destruction by a single catastrophic event (Ono et a1. 1983). Human activities have posed potential and realized catastrophes in Death Valley. Early in the 1900s, construction of the Los Angeles Aqueduct greatly modified habitats in the Owens River drainage. New dams reduced flooding that had created killifish habitat, marshes were drained, and game fishes (e.g., brown trout and largemouth bass) and mosquitofish were introduced. The game fishes used small native fishes as food, and the mosquitofish competed with some of them. Use of groundwater for crop irrigation disrupted fish habitat and lowered water tables on which fish depended in the Amargosa Valley and Ash Meadows. Introduction of nonnative fishes to waters of Ash Meadows also presented problems for its native fishes. These threats were particularly devastating for killifishes. The Devils Hole pupfish, which exists only in a small spring pool called Devil's Hole in Ash Meadows, was particularly affected by groundwater with- drawals (Figure J5.2). Lowering water levels gradually reduced photosynthesis in its limited habitat and exposed a shelf on which it depended for spawning substrate and its algal food supply. To forestall threats to Death Valley fishes, wildlife agency personnel met in 1969 to develop an integrated plan for their preservation. The Desert Fishes Council, which continues to be active today, was established at a 1970 meeting at the Death Valley National Monument headquarters. Consisting largely of state, federal, and academic biologists, it has assumed a strong role in coordinating preservation efforts and assisting government agencies with preservation pro- grams. Various strategies have been employed to preserve Death Valley fishes. Several fishes were transferred to natural or artificial refugia. The Devils Hole pupfish, for example, was first transferred to five refugia in California and Nevada and to an artificial refugium built by the Bureau of Reclamation below Hoover Dam. The latter transfer resulted in phenotypic changes in the fish (Williams et a1. 1988). Later, a fiberglass shelf was suspended below the surface of its pool and artificially lighted to enhance algal production. The fish was also reared in aquaria, ............