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.1 ~ - 3 - Habitat mapping will also be done in the areas used by radiotagged fish during tracking, prior to spawning. The purpose of this mapping is to establish habitat use prior to spawning, and to determine if staging is a critical element to the spawning event. The habitats delineated on AutOCad digitizing program. and percent of each habitat the acetate overlays will be quantified using an This system will be used to assess the surface area type, as well as changes in area by flow. The primary purpose of this investigation is to identify and describe spawning sites and nursery areas of humpback chub in Westwater Canyon, and to determine spawning flow requirements. Once a spawning site is identified, complete documentation will be developed for the area inCluding measurements of depth, velocity, substrate size, cover, and water temperature. These parameters will be recorded to quantitatively describe the spawning site and nursery area. Also, the site will be mapped for habitat types at the spawning flow, at the peak of runoff, at base flow, midway between base flow and runoff, and at the flows observed during radiotracking. This approach will be used to establish a relationship between flow and surface area of spawning and associated habitats, in a similar analysis to that performed by Carter et al. (1985) for fish habitat of the Colorado River near Parachute, CO. The analysis involves developing mathematical relationships between flow and each habitat type, based on the surface area of each. Those mathematical relationships will be 1eveloped over the 3 years of the study, and have associated with each, Ir' values, or coefficients of determination. These mathematical relationships are proposed as the principal tool for determining spawning flow recommendations for humpback chub in Westwater Canyon. In addition to determining the spawning-flow requirements as outlined above, an effort will be made to determine the environmental and water quality parameters that prompt the humpback chub to spawn at a given time. We hypothesize that the timing of spawning is determined by a combination of environmental factors, including water temperature and cumulative temperature degree days. Ongoing river flows and temperatures will be secured from the USGS Stateline Gaging Station located on the Colorado River about 15 miles upstream of the proposed study area. No major influences occur between the gage and the study area, and it is expected that this station will accurately represent conditions in Westwater Canyon. TASK 2: DETERMINE EXTENT OF LARVAL DRIFT Subtask 2A: Deploy Drift Nets. The mechanism by which larval humpback chub emerge from their egg and find their way to suitable nursery habitat is unknown. In contrast to larval Colorado squawfish, which may become transported for many miles by river currents, the fidelity of the humpback chub to specific regions of river probably precludes long distance drift for this species. If long distance drift did occur, large numbers of young chubs would be expected in regions far downstream of population concentrations such as Black Rocks and Westwater Canyon. This does not seem to be the case. Hatchery personnel also report distinct behavior for swim-up chubs that will be further investigated. Drift of larval humpback chub will be monitored immediately below identified spawning sites to confirm the site and to ascertain the age at which the fish drift, as well as the distance. A minimum of four shoreline and four midchannel drift samples will be taken using the drift nets and techniques described by Haynes et a1. (1984) and Yaldez et a1. (1985). The shoreline sets will be positioned with rebar driven into the shore below the spawning site. The midchannel samples will be taken from the motorized rafts towing a bongo type net