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I I I I I I I I I I I I I I I I I I I ~' It\' ji !!f. i f" ~ s: ~. - 5 growth and development is usually short, food is rarely limiting due to substantial increases in allochthonous input and increased access to fringing and connected slack- water habitats. Predators are relatively scarce due to a dilution effect of increased habitat space during flooding (Bayley 1988; Winemiller 1989). Predation and resource limitations come into play afterward, when juveniles are concentrated in the channel as floods recede. Adult populations may remain relatively stable, while juveniles suffer severe mortality with few ultimately surviving to recruit. Many species are considered flood exploitive and year class strength is positively correlated to discharge (Ross and Baker 1983; Welcomme 1985). Many of these species, particularly those that are widely dispersed, may persist as meta-populations with the spatial arrangement of habitat features acting as a template of organization (Schlosser and Angermeier 1995; Stanford et al. 1995). Such metapopulation structure may be the rule for many salmonid species (Rieman and McIntyre 1993). The heterogenous mosaic of floodplain vs. constrained reaches combined with local events result in local successes and extinctions for populations which are then recolonized from adjacent populations (Stanford et al. 1995). Similarly, many habitats may only support one life-history phase and represent sinks which are continually recolonized from other sources (pulliam 1988). As in other highly seasonal systems (Urban et al. 1987 ; Walker et al. 1995), the natural, temporal regime of variation and disturbance of the Colorado River has been dramatically altered by human intervention. Where not reservoir dominated at present, the system is far more typified than before by longitudinal processes proposed for a river