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Accession Number 5004024

Title Effects of instream flow depletion on biological integrity of stream fish communities

Project Description In order to construct instream flow guidelines that will protect biotic integrity of streams, managers

need to understand how biotic assemblages may change when flows are variously altered to

meet human needs. This research will address this need by assessing fish assemblages in a

sample of Georgia streams that are variously affected by water withdrawals or upstream

impoundments. The project is a cooperative effort with the Georgia Wildlife Resources Division

(WRD), and will provide specific data relating the integrity of native fish assemblages to degree of

streamflow alteration. We will sample fish assemblages in approximately 40 stream segments in

the Piedmont ecoregion of Georgia, including reference (least impaired) streams and segments

that are variously affected by water withdrawals or diversions. We also will assess instream

habitat conditions in each sampled segment. Fish assemblage data will be used to score sites

according to an Index of Biotic Integrity (IBI) developed for Piedmont streams by GA WRD. Total

IBI scores and individual metrics (e.g., species richness, relative abundances of sensitive or

intolerant species) will be plotted against measures of hydrologic alteration for each stream

segment. Degree of hydrologic alteration will be assessed from the magnitude of seasonal water

withdrawals expressed as a proportion of average unimpaired flows. Regression and correlation

analyses will be used to describe relations between fish assemblage characteristics and

hydrologic alteration. We will use results to construct predictive models of fish assemblage

response to streamflow depletion. We will use measures of instream habitat at low flows to infer

potential habitat-related mechanisms linking flow depletion and fish assemblage changes.

Keywords biotic integrity, hydrologic alteration, instream flow, stream fishes,

Principal Mary C Freeman, USGS Patuxent Wildlife Research Center: mary_freeman@usgs.gov;

Investigators

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