We studied recovery processes for 3 yr in Quartz Creek (Cascade Mountains, Oregon), a third-order stream catastrophically impacted by a February 1986 debris flow for which both predisturbance data and an upstream control reach were available. The debris flow altered channel geomorphology and destroyed riparian vegetation for 500 m, resulting in a reach with short, disordered channel units, low hydraulic retention, and an open canopy. High irradiance levels and reduced grazing by macroinvertebrates contributed to rapid accrual of benthic algae in the disturbed reach, which formed the bioenergetic basis for ecosystem recovery. Macroinvertebrates (mostly herbivores) recovered to upstream densities and taxonomic richness within 1 yr, although effects on community structure persisted into the second year. Cutthroat trout (Oncorhynchus clarki) populations were locally decimated by the disturbance, but by the following year, recruitment of young-of-the-year trout into the reach exceeded that of the upstream reach and populations had recovered to predisturbance densities. Despite the general rapid recovery of the biota within the disturbed reaches, most populations showed broad temporal fluctuations in abundance, suggesting that ecosystem stability was diminished by the debris flow. Long-term monitoring of Quartz Creek may yield additional insight into the role of episodic disturbance in stream ecosystems.

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Emergent cutthroat trout fry (Salmo clarki) were observed in the margins, backwaters, and side channels, collectively called "lateral habitats," of three study streams with different riparian vegetation. Most fry remained in these lateral habitats until the end of their first summer. The abundance of cutthroat fry was proportional to the area of lateral habitat in each of the study streams. Average size and growth rate of fry were related to the effect of site elevation on stream temperature and the influence of riparian vegetation on the availability of invertebrate food. Lateral habitats are characterized by slow, shallow-water, abundant detritus and benthic invertebrate assemblages of high density. Stream margins and backwaters provide gradients of depth and velocity, cover, and access to food that are appropriate to the habitat requirements of fry. Because fry populations are closely related to the abundance and quality of lateral habitats in small streams, these habitats should be included in the assessment of habitat requirements of cutthroat trout.

In Mack Creek, a third-order stream flowing through a 450-year-old coniferous forest in Oregon's Cascade Mountains, population size of young-of-the-year cutthroat trout Salmo clarki was positively correlated with length of stream edge and area of lateral habitat. Lateral habitats included backwaters and eddies at the margin of the channel that made up 10-15% of total stream area. Lateral habitat area was reduced at higher or lower streamflow, but the length of channel perimeter formed by lateral habitats was never less than twice the length of the reach. In an experimental manipulation of lateral habitat before the emergence of young fish from the redd, an increase in lateral habitat area of 2.4 times the area observed in control reaches resulted in a 2.2times greater density of age-0 cutthroat trout. Young-of-the-year fish were virtually eliminated from stream sections with reduced area of lateral habitat. Growth was not affected by the greater density of fish in reaches with enhanced lateral habitat.