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<br /> <br />Figure 6.-Surber sampler. Photo 801-0-79667 <br /> <br />ficulty of sealing the bottom against an irregular <br />surface. and its limited use in very high or low <br />flows, this sampler was selected for this study <br />because it is primarily designed for collecting <br />macrofauna inhabiting gravel-and cobble-type <br />substrates. The upper Arkansas River contains a <br />predominance of this type of substrate. Artificial <br />substrate samplers could have been used; <br />however, LaBounty et al. (1975) 1941 reported <br />a loss of artificial substrate samplers due to van- <br />dalism in a previous study in the upper Arkansas <br />River. <br /> <br />After the collection of a macroinvertebrate sam- <br />ple, it was placed in a white porcelain pan. <br />Forceps and a small aquarium net were used to <br />separate the organisms from debris. All samples <br />were initially preserved with a 10-percent solu- <br />tion of formalin. After the organisms were iden- <br />tified and counted in the laboratory. they were <br />preserved with a 90-percent ethanol solution for <br />storage. <br /> <br />Only riffle areas were sampled for macroinverte- <br />brates due to the varying water depths and <br />velocities in the upper Arkansas River. At each <br />station a composite of three random Surber <br /> <br />samples from a transect within the riffle area <br />were collected and preserved on each sampling <br />date. <br /> <br />Electrofishing was determined to be the most <br />appropriate method for obtaining fish due to <br />shallow waters, uneven substrate, and low <br />numbers of fish. Collections were made using a <br />115-volt Coffelt Model BP-2 backpack elec- <br />troshocker. Selected river sections approximate- <br />ly 1 50 m in length were sampled during the fall <br />of 1979. Shocking was done while wading <br />upstream and the fish collected were placed in a <br />portable aluminum holding cage submerged in <br />the river. All fish were measured and recorded <br />by species. <br /> <br />A mark-recapture method of population estima- <br />tion was used. Fish were collected, marked by <br />operculum punch or fin clipping. redistributed <br />within the 1 50-m stream section. and the river <br />section electrofished a second time. A selection <br />of fish from each station was eventually retained <br />and the livers were excised and frozen immedi- <br />ately for laboratory analyses of selected heavy <br />metals. <br /> <br />18 <br />