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BIOGEOGRAPHY OF THE SALTON SEA
- University of California Press
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Biogeography of the Salton Sea I O C E O C R A P H Y ENCOMPASSES howledge and inferences of both past and present . It is challenging to deduce how present conditions affect dlstributions and abundances of a suite of organisms, to say nothing of how past condltlons might be related to present ones. Here we compare what is known about the fauna of Lake Cahuilla with what is known about the fauna of the Salton Sea In order to put current dlstributions into perspective. But geographycan only provide part of the story, so we descnbe current vegetation and habitats to clarify many patterns that might otherwise remain mysterious. THE FAUNA OF LAKE CAHUILLA That Lake Cahuillawas born from ColoradoRiver floodwaters is attested by its similar fish fauna. Unlike the current Salton Sea, which supports only game fish (Walker et al. 1961; Riedel et al. zooz), Lake Cahuilla supported a fish community that was clearly a subset of the community on the lower Colorado River (Gobalet 1992).It included such species as the Razorback Sucker (Xyrauchen texanus), the Colorado Squawfish (Ptychocheiluslucius),the Striped Mullet (Mugil cephalus), the Machete (Elops aflnis), and the Bonytail (Gilaelegans; Gobalet 1992).The floodwaters that filled the Salton Sea also brought other species, such as the trout Salmopleuriticus and the nonnative carp Cyprinus carpio (Evermann 1g16),but none persist today (Walker et al. 1961;Saiki 1990).Aquatic mammals typical of the Colorado River valley are also known to have been present in Lake Cahuilla.For exarEple, the Muskrat (Ondatrazibethicus)occurred at Lake Cahuilla (Yohe 1998), and it occurs today in freshwater marshes flanking the Salton Sea and in lakes in the Imperial Valley. Little is known about the avifauna of Lake Cahuilla, although there is every reason to suppose that it was very similar to that of the present Salton Sea (Patten and Smith-Patten 2003). Indeed, given the ancient lake's vast size, it was perhaps even more heavily visited by species now generally confined to the Gulf of California . Evidence from archaeologicalmiddens provides a partial picture of the bird life of Lake Cahuilla. As expected, present-day species such as the Eared and Pied-billed Grebes, the Aechmophorus grebes, the American White Pelican, the Black-crowned Night-Heron, the Anas and Aythya ducks, and the American Coot were all in evidence at Lake Cahuilla (Wilke 1978; Beezley 1995; Patten and Smith-Patten 2003).Given the preponderance of immature American Coots captured, it is obviousthat the species bred cornmonly at Lake Cahuilla. Furthermore, there is evidence of a heron rookery at Bat Ca.ve Buttes (Willze1978:102),a former island to the southeast of North Shore, a few kilometers east of the railroad stop at Durmid. Of course, presence in a midden is only an indication of .what was hunted and thus does not provide a complete portrait of the birds on the lake. For example, shorebirds were "apparently not sought by inhabitants of the Myoma Dunes" (Wilke 1978: 92), even though they were likely abundant at Lake Cahuilla; thus, there is scant evidence of their occurrence. Some speciescollectedfar from Lake Cahuilla were transported to settlements along the shore; such transport presumably explains the two Band-tailedPigeons in tlle Myoma Dunes midden (Wilke 1978:97). Nonetheless, midden evidence supports the notion that prehistoric species composition was simjlar to that oftoday (Table2; Patten and Smith-Patten 2003). CURRENT CONDITIONS Situated in the heart of the western Sonoran Desert, the Salton Sink typically has hot, dry weather. Despite occasional thunderstorms froni the south, summers are particularly hot. For example, the maximum temperature exceeds 100°F on IIO days a year in the Imperial Valley (Hely and Peck 1964). Temperatures average slightlylower in the CoachellaValley. Conversely, rainfall is slightlyhigher in the Coachella Valley, although the entire sink gets little ai~nual precipitation , with a mere 7.6 cm a year at Mecca (Hely and Peck 1964).Most rain falls;from December through mid-March; it has rained only once in June since 1914 (Layton and Ermak 1976).Even so, it is often humid because of the extreme evaporation from the sea and the surrounding irrigated agricultural lands. Finally,the deep rift of the San Gorgonio Pass forms a natural funnel. Gusty winds and sandstortns are frequent in the northern Coachella Valley, but the Salton Sink is less affected. The Coachella and Imperial Valleys remain among the most important agricultural areas in the United States, with crops ranging fiom grapes, dates, and sugar beets to Alfalfa, cotton, and...