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cascades. Interspersed amongst this structure are broad sandbars and other depositional features more typical of erosive southwestern streams. These shift seasonally (and dramatically) according to duration and extent of flooding. Dominant riparian vegetation is a mixture of native [Catclaw acacia (Acacia greggii), Honey mesquite (Prosopis qlandulosa), Coyote Willow (Salix exigua), Arrowweed (Tessaria sericea)), and nonnative species [Tamarisk (Tamarix chinensis), Camelthorn (Alhagi camelorum)) (Carothers and Brown, 1991; Johnson, 1991). Giant reed (Phragmites australis) and cattail (Typha spp.) occur patchily. The lower LCR passes through a narrow gorge that progressively widens and deepens as it drops towards Marble Canyon. A series of precipitous travertine falls at RKM 14.9 (Atomizer Falls, Fig. 1--2b) mark upstream distribution of G. cypha. Base camps.---Three base camps were established in the LCR gorge: Near its confluence (RKM 0.55); at Powell Canyon (RKM 3.1); and at Salt Canyon (RKM 10.8). Biologists worked from each camp. Those at the confluence fished the lower 1.2 km of river, while those at Powell camp fished upriver from 1.3--7.0 km. Salt camp personnel fished from 8.0--14.9 km. Data collection.---Fishes were captured during 19 6--14 day trips at approximately monthly intervals from July 1991 to December 1992. Hoop nets (0.76 or 1.2 m dia., 2.4 or 3.0 m length, four- or six-hoop, single- or double-throat) were deployed in all available habitat types of sufficient depth (i.e., > 0.4 m). Trammel nets (7.6 to 45.7 m length, 1.8 m depth, 1.3 to 3.8 cm inner and 30 cm outer meshes) were set routinely in the confluence. Fishing effort for a particular trip was recorded as number of net-hours per camp. All captured fishes were identified, measured (TL to nearest mm) and weighed (nearest g). Native species were examined for tags, markings, secondary sexual characteristics, ripeness, and general health and condition. Those greater than 150 mm TL 'adults') were injected with passive integrated transponder (i.e., PIT) tags (see Prentice et al., 1990) and released near points of capture. Nonnative fishes were scanned for presence of PIT tags (a result of consuming tagged native fishes), then sacrificed and either dissected immediately or preserved for later study. Analytical protocol.---One-way ANOVA (Proc GLM; SAS, 1985) was used to compare total fishing effort and captures of adult G. cypha by reach and year. To determine movements during 1992 (which represented a full year of sampling), adult chubs were grouped by reach and season (winter = December, January, February; spring = March, April, May; summer = June, July, August; and autumn = September, October, November). Numbers of G. cypha tagged/recaptured in a given reach during a given trip were 3