GAP analysis of fish in the hydrologic unit 12090205 of central Texas

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Title: GAP analysis of fish in the hydrologic unit 12090205 of central Texas
Author: Wang, Fajin
Abstract: GAP analysis has been successfully used to predict the biodiversity and develop conservation priorities on land on a broad scale since 1987 . Its application to aquatic ecosystems started in New York in 1995 on a watershed scale and in Missouri in 1997 on a statewide scale . No complete standard method is currently in use . This project attempted to apply GAP analysis to the eight -digit hydrologic unit 12090205 of the Colorado River basin in central Texas to identify and prioritize opportunities for conserving fish biodiversity in the riverine ecosystems , and to demonstrate the feasibility of applying tiie GAP analysis approach to the aquatic ecosystem in Texas . The regular GAP analysis procedures were followed in the study . Sampled fish data were compiled and put into a customized Microsoft Access® relational database . The watershed -wide "known" distribution maps were produced by geographically linking each sample to the National Hydrologic Dataset (NHD ) which allows the graphical display of sampling locations , and spatially cross -referencing these data in a tabular format . The riverine ecosystems were classified into Valley Segment Types using ArcGIS® (Environmental Systems Research Institute , Inc ) . The eight variables for the classification were Size , Size Discrepancy , Gradient , Valley Wall Interaction Points , FIow , Rocktype , Floodplain and Land Use /Land Cover . Additional auxiliary attributes , Lowland , Soil pH , Pool , Lake , Backwater , Gravelpits , Mouth and Sewage , were also assigned to each segment . Habitat affinities were compiled and extracted from a number of available sources . New habitat -affinity information was also generated from the sampling database in conjunction with the valley -segment datalayer . Habitat -affinity models were then created using Structured Query Language (SQL ) and were used to predict species occurrence on valley segments for each species known to occur in the study area . Logistic -regression models also were developed and employed to predict of species occurrence for the purposes of references and comparison . The variables Water Quality , Land Use /Land Cover , Road /Rail Road and Dam were used to classify the valley segments to develop an index of environmental quality for fish . The environmental quality index , the predicted fish biodiversity and the number of fish species of special concern (i .e . , endemic to Texas , endangered /threatened and with a state rank from S2 to S4 ) were combined to develop tiie conservation priority ranks for each segment . The segments with a prior conservation rank were calibrated with the current conservation status and feasibility . The results show that I ) the segments with high environmental quality are in Barton Creek , in the upper portion of Onion Creek and in the Balcones Canyonlands ; 2 ) predicted fish diversity is expected to be highest in midsized streams ; and 3 ) three groups of segments were identified as candidate conservation sites . They are i ) the lower portion of Barton Creek , ii ) the group of segments including three segments of Colorado River , Coldwater Creek , and three adjacent segments , and iii ) two lower segments of Onion Creek and two segments of Colorado River right downstream of the City of Austin . The segments with high conservation priority after calibration are in the second group , and they are the gap for conservation ; 4 ) the GAP analysis approach used in this study was shown to be a feasible method for developing conservation priorities in central Texas .
URI: http : / /hdl .handle .net /2346 /20402
Date: 2004-12

Citation

GAP analysis of fish in the hydrologic unit 12090205 of central Texas. Master's thesis, Texas Tech University. Available electronically from http : / /hdl .handle .net /2346 /20402 .

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