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<br />Sampling Methods <br /> <br />All samples were collected using standard techniques (U.S. "Geological <br />Survey, 1977). Stream-water samples were obtained using an epoxy-coated <br />US DH-48 or US D-49 sampler and depth-integrating procedures (Guy and Norman, <br />1970; Edwards and Glysson, 1988). Water samples from reservoirs were collected <br />using a polyvinyl chloride Van Dorn sampler. Depth profiles of specific <br />conductance, pH, temperature, and dissolved oxygen were measured at the time <br />of sampling. All water samples were passed through a 0.45-~m filter and <br />preserved at the sampling site. <br /> <br />Bottom-sediment samples from stream and reservoir sites were collected <br />using a US BMH-60 sampler that had a stainless steel scoop. Samples from <br />several locations at each site were composited in a stainless steel bucket, <br />and a subsample was removed using a wooden spoon. At some shallow stream <br />sites, bottom sediment was scooped directly into the bucket using a wooden <br />spoon. Bottom sediment was not sampled at the Arkansas River above Pueblo <br />(site AI) because the streambed was completely armored with coarse cobbles. <br /> <br />Variable numbers of adult and prefledged mallards, American coots, and <br />other bird species were collected by taking birds from nests or by shooting <br />them with steel shot. Livers of individual birds, or composites of three <br />livers from killdeer, were analyzed for inorganic constituents. Two liver <br />samples each of mallards and killdeer from all reservoir sites, except the <br />Great Plains Reservoirs, were analyzed for organochlorine pesticides and <br />PCB's. Two liver samples of double-crested cormorants 'from John Martin <br />Reservoir also were analyzed for organic constituents. Samples of breast <br />muscle and livers from the same individual birds were analyzed for inorganic <br />constituents to assess the use of livers to predict concentrations in breast <br />muscle. Breast-muscle concentrations may be of interest to human health <br />authorities. In addition, whole or partial clutches of eggs of several bird <br />species were collected during the nesting season at each reservoir site and <br />analyzed for inorganic constituents. <br /> <br />One or more fish species were collected by using gill nets at reservoir <br />sites and electroshocking equipment at stream sites in accordance with standard <br />procedures (U.S. Fish and Wildlife Service, 1985). Species collected at <br />stream sites were mostly bottom-feeding omnivores, including carp and suckers. <br />Species collected from the reservoirs included bottom-feeding omnivores <br />(typically carp), carnivores (typically bullhead catfish, bass, or walleye), <br />and filter feeders (typically gizzard shad). For each species, three individ- <br />ual fish of similar length were composited, producing one sample of a species <br />,per site per sampling period. Each sample was analyzed for inorganic constit- <br />.uents. Samples of two species each from Pueblo Reservoir and Lake McKinney <br />were analyzed for organochlorine pesticides and PCB's. Samples of common carp <br />from stream sites A2, A3, AS, and A7 also were analyzed for organochlorine <br />pesticides and PCB's. <br /> <br />Composite samples of an abundant invertebrate species (typically cray- <br />fish) and an abundant species of submerged aquatic vegetation (typically <br />algae and pond weed) were collected, where available, at reservoir sites <br />during the June sampling period. The species varied among the sites. Whole <br />crayfish were obtained with electroshocking equipment, and several individuals <br /> <br />26 <br />