8142

• UCREFRP Catalog Number: 8142
• Author: Horn, M. J.
• Title: Nutritional Limitation of Recruitment in the Razorback Sucker ‎(
• USFW Year: 1996.
• Copyright Material: NO

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6

continuum. by Vannote et al. (1980). Dams create serial discontinuities creating stretches

of the river that ecologically behave similar to lower order, headwater systems. (Ward

and Stanford 1995a). Productivity has shifted toward autochthonous processes and away

from fonnerly dominate allochthonous input/transport processes (Liebennan and Burke

1993; Ward and Stanford 1995b). Lateral exchange of nutrients and organic materials

(Bayley 1988; Junk et al. 1989), fonnerly a function of the floodplain facilitated by

flooding, has been lost due to stabilization of discharge and artificial channel constraints

(Holden 1979). Habitat heterogeneity has been greatly decreased with the loss of many

highly productive fringe and low-velocity habitats (Stanford 1994). Further, numerous

introduced fishes now occur that may be better adapted to the new environment

(Laurenson and Hocutt 1985; Hendrickson and Brooks 1987). In all cases where such

habitat change and introductions are coincident, native biota declines (Hubbs 1972; Bain

et al. 1988). Adults of long-lived fishes like razorback suckers may persist in modified

habitats (Cole 1954; Minckley 1983, 1991), but larval/juvenile stages disappear
(Nikolskii 1969; Minckley et al. 1991) and extinction ultimately ensues.

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2. The Colorado River

The Colorado River of west em North America drains some of the most arid landscape in

the World. The river nonetheless supplies a greater percentage of its water for

consumptive use than any other watershed in the United States (pillsbury 1981), and is
considered the world's most regulated river (Plummer 1983). Less than 1.0% of the

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