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<br />evaporation) were utilized from March to June to collect stoneflies at <br />the Pipe Creek and Fisher River sites. Light traps were operated nightly <br />from June to October, 1980 at the Pipe ~reek and Fisher River sites to <br />collect caddisflies and dipterans. The light traps contained uv fluorescent <br />lights powered by 110 volt A.C. current or by batteries controlled by <br />a photocell which activated the lamp during the hours of darkness. <br /> <br />Insect drift nets had a rectangular opening measuring 45.7 by 30.5 <br />cm and a Nitex bag 1.5 meters long made of 355 ~m mesh. The frame was <br />made of angle iron with holes for steel rods which were dri'. ~'l into the <br />substrate. Samples were taken in dupl icate; two nets were set parallel <br />to each other and to the shoreline in water from 15 to 30 cm deep. Flow <br />rates through the nets were monitored with a current meter. Generally <br />the nets were set for a period of one hour. <br /> <br />Continuous recording thermograph data were obtained from the U.S. <br />Army Corps of Engineers. Flow and chemical data were obtained from the <br />U.S. Geological Survey (USGS) for the Kootenai River station below Libby <br />Dam. Temperature and flow data from the Fisher River were obtained from <br />USGS. Temperatures of Fisher River recorded in water year 1976 and Kootenai <br />River in water year 1980 are shown in Figure 2. <br /> <br />Periphyton standing crop was quantified at the sampling stations <br />on a seasonal basis (August, October and January) by measuring ash-free <br />dry weights and chlorophyll a on material collected from natural substrates. <br />For ash-free dry weight analyses, the Aufwuchs layer was removed from <br />a randomly selected rock and the surface area was measured. Replicate <br />samples were taken at two depths. Chlorophyll a samples were taken by <br />scraping periphyton from a 6 cm2 area using a flexible template. The <br />sample for analysis of chlorophyll a was placed in an opaque, screw- <br />cap centrifuge tube, and frozen untTl it was extracted. Methanol was <br />used in the extraction process (Holm-Hansen and Riemann 1978); calculations <br />were made according to Lorenzen (1967) using experimentally determined <br />absorption coefficients (Riemann 1978). <br /> <br />Benthic community metabolism was measured at the Dunn Creek and <br />Fisher River stations in September, 1981 by placing rocks from a circumscribed <br />area of the riverbed in recirculating chambers used in ~itu and recording <br />changes in oxygen evolution. Calculations were made of gross productivity, <br />net community productivity, 24-hour respiration, net daily metabolism, <br />and the productivity-respiration ratio. <br /> <br />Organic carbon in the seston was quantified as particulate (POC) <br />and dissolved (DOC) on a monthly basis for the first year of the study. <br />Analyses were conducted according to Menzel and Vaccaro (1964) in which <br />organic carbon is oxidized and quantified in an infrared detector (Ocean- <br />ography Interna t i ona 1, Inc.). In order to determine how the part i c 1 e <br />sizes which are available to insect filter feeders are altered by river <br />regulation, the particle component of the seston was size-fractionated <br />on a seasonal basis (September, November and February) at the control <br />and regulated sites. A wet filtration method was used to size fractionate <br />samples of the seston, and the organic carbon content of each size class <br /> <br />-4- <br />