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Communication at the NABS Annual meeting, Keystone, 2000
(320) DISTRIBUTION, ABUNDANCE, AND DRIFT RATES OF INSTREAM FLOW INDICATOR INSECTS IN THREE RIFFLES ALONG THE GUADALUPE RIVER ,TEXAS.
L.R.T. Tolley1, R.E.M. Moss2, and T.L.A. Arsuffi1. 1Department of Biology-Aquatic Station, Southwest Texas State University, San Marcos, Texas 78666, 2River Studies, Texas Parks and Wildlife Department, San Marcos, Texas 78666
Historically, fish communities were used to determine instream flow requirements of rivers. However, in this study, we developed criteria for selection and examined the application of "indicator" aquatic insects in determining flow requirements for the Guadalupe River, Texas. The insects used were: Neoperla clymene (Plecoptera), Isonychia sicca (Ephemeroptera), Corydalus cornutus (Megaloptera), Cryphocricos hungerfordii (Hemiptera), and 6 genera of Elmidae (Coleoptera). These insects are restricted to riffles, where most impacts by changing hydrologic conditions occur. Response of the indicator insects to flow and habitat variation associated with depth, velocity, and substrate composition, was determined by collecting 25 quantitative benthic Hess samples from 3 riffles along the river and from a diel drift study that took place at each of the 3 riffles at three time periods during the summer of 1999. Results of the drift study showed all indicator insects exhibited the same drift tendencies of no or limited drift until the hours of midnight to 0300 in which a peak density was observed. The drift patterns of all indicator insects appeared to be independent of daily flow fluctuations caused from hydropower plants along the river. Benthic results showed the indicator insects used specific velocity and substrate ranges, but had no preferences for a specified water depth.
Presented at 3:30 PM on Thursday, June 1, 2000 in Integrating Physical, Chemical, and Biological Indicators of Water Quality II
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