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PVC collection buckets (10-cm diameter). Each net had a 560 u mesh, a length of 4 m and an open-mesh to net mouth ratio of 11:1. This design enhances self-cleaning and filtration efficiency of the net theoretically approaches 100% (Faber 1968, Tranter and Smith 1968). Attached to each net frame was a removable 4-point, steel cable bridle assembly terminating in a spring-loaded carabiner. Nets were deployed either by staking the net frames to the substrate or by fastening the bridle carabiner to a polypropylene line fixed to either an instream boulder or a metal post driven into the shore. Drift-net (ichthyoplankton) sampling in the Colorado River study area was conducted in the Black Rocks area (km 219.8 to 218.2) at dawn, dusk, and midnight using 3 nets during each collection period. Sampling duration ranged from 30 minutes to 1 hour/set depending upon accumulation of sand and organic debris in the collection buckets. A Marsh-McBirney flowmeter (Model 201) was used to measure water volume filtered by each net. An attempt to attach nets to a cable stretched the full width of the river was abandoned for safety reasons. In the Yampa River study area, only 1 net was used/site due to restricted storage space in the inflatable raft used to travel within the area. Drift sampling was conducted in conjunction with regularly-scheduled random sampling and sampling times per date varied; however, approximately equal numbers of nocturnal and diurnal collections were taken over the period. Sampling duration varied from 30 minutes to 7 hours depending upon the amount of organic debris and sand accumulation. Water volume filtered by the net was measured with a pygmy flowmeter (Gurley Model 625 F). Samples were preserved in 10% formalin and returned to the laboratory for sorting and analysis. Specimens were stored in 3% buffered formalin. Specimens were identified to the lowest feasible taxon, counted, and measured to the nearest 0.1-mm total length (TL). Since reliable criteria for the differentiation of YOY and juvenile chubs (including hybrids and/or intergrades) are not yet available, all ch~~bs were listed as Gila spp. Drift rates were computed as number/1,000 m3. A nonparametric permutation technique (Mielke and Iyer 1982) was performed on Colorado River data to compare drift densities (response variable), collectively, and for predominant taxa, among the 3 sampling times (treatments) over the entire sampling period. Lack of replication and sampling time variability did not permit a similar analysis of Yampa River drift data. RESULTS AND DISCUSSION A total of 694 individual collections (seine and drift net) was made in both study areas combined (Table 1). In the Colorado River, 384 samples were collected between 5 March and 27 August, 1982. In the Yampa River, 310 samples were collected between 18 April and 23 October, 1982. Due to a rafting accident, 46 Yampa samples collected on 8-11 June, were lost. Preliminary sorting and analysis of 1982 samples are complete. Data have been stored on the Fish and Wildlife Service MANAGE database program at Colorado State University, Fort Collins. The current status of MANAGE data files from 17 March, 1981 to present are shown in Table 2.