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5-4 5.2 Weekly Drift Densities One of the main objectives of this study was to assess the species composition and relative density of drifting larval target fishes at the headgates of the proposed JH-1 project. Although no T&E fishes were captured, the results of the investigation are ,nevertheless, presented. Using the techniques described in the METHODS section of this document, the drifting density of each species captured in each drift net sample was estimated and is presented in Table B-2 of Appendix B. Maximum drift density for a single species in a given drift net sample was 2.480 fish/1000 cubic feet of water. Mean weekly densities and standard deviations of these values for the 9-week sample period are presented in Table B-6. Variations in the weekly mean drift densities appear to be related to river discharge and water temperature (Figure 3). Few fish were found drifting before and at the initiation of the drift net sampling on July 13, 1984, based on preliminary sampling and measurements of water temperature. Drifting fish were first detected the second week of July when water temperatures first reached 16.0 C. The trends in densities of drifting fishes followed closely trends in water temperature. Mean weekly densities increased from 0.1633 fishes/IOOO cubic feet of water in the first week of sampling to a peak of 2.3385 fishes in the third week as river temperatures rose from 16.5 to 20.5 C and discharge decreased from about 18,000 to 10,000 cfs (Figure 3). The continued warming and decreased discharge of the river in the fourth week of sampling, however, did not result in increased drift densities; mean weekly drift density at that time dropped to only 0.3050 fishes as the river temperature peaked between 20.5 and 21.0 C. Valdez and Carter (1983) reported a similar phenomenon 35 river miles upstream, as drift densities increased and peaked during increasing river temperatures but dropped off