7726 - Laserfiche WebLink

Home Browse Search

.. ... S+anForo + lt~an:J I q~(pb- .A.~, __0 t"/r")~6 r 0-1- CL41 +-tJ vd qL WcJ Y"4 )q9~h- 9B. Fish of the Colorado system 1. A. Stanford &1. V. Ward Introduction The abundant remains of large minnows (Cyprinidae) in caves near desert segments of the Colorado system (Plate Ic, e; cf. Minckley 1973), suggest that the riverine fish were important sustenance for prehistoric man, The river continues to supply sustenance, but the modes of transfer have changed dra- matically. The vicarious regulation of the Colorado River, coupled with many introductions of non-native species, has caused precipitous declines among the indigenous fish, This chapter describes the indigenous fish fauna and its relation to the physiographic and hydrographic history of the basin (Stanford & Ward 1986a: Fig. 1), and includes consideration of species in parts of the Colorado system affected by desertification (e.g. Pluvial White River, Railroad Valley: Hubbs & Miller 1948). We also indicate the status of the native fish in the regulated river, and discuss the impacts of exotic species. The native fish fauna Thirty-two species of fish in seven families are indigenous to the Colorado system (Table 1). Several have diversified in isolated local or sub-basin popu- lations. Thus, four forms of the Colorado River chub (Gila robusta) are recog- nised in the Gila, Virgin and Pluvial White rivers (Rinne 1976; Smith et al. 1979). Two subspecies of the spinedace (Lepidomeda mollispinis) are isolated in the Virgin River and Meadow Valley Wash (Lee et al. 1980). Minckley (1973) listed four subspecies of the desert sucker (Catostomus clarki) in Lower Basin tributaries. Five subspecies of White River springfish (Crenichthys baileyi) are isolated in desert springs in the Pluvial White and Moapa drainages (Deacon & Bradley 1976; Williams & Wilde 1981), The speckled dace (Rhinichthys osculus) is the most widespread native species, but populations in different sub-basins The Ecology of River Systems, edited by 8, R, Davies & K. F. Walker i] /986. Dr W. Junk Publishers, Dordrecht, The Netherlands ~ .- ~ t --< ~ ~~,.... , .. ..... ~ 0 ~, 'V~, .... 7 :. .;..~ ~ 385