Spatiotemporal Patterns of Fish and Aquatic Insects in an Increasingly Urbanized Watershed of Central Texas




Shattuck, Zachary R.

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Aquatic systems in the Edwards Plateau region of Central Texas provide habitat for a large number of endemic fauna. Within the last decade, the Edwards Plateau region has experienced rapid human population growth and the effects of urbanization on water quality and quantity is a growing concern. Purposes of this study were to quantify aquatic insect communities and fish assemblages in the relatively undisturbed Pedernales River drainage of the Edwards Plateau, to assess factors influencing species occurrence and distribution through time, and identify current impacts of urbanization due to a number of land use changes and in-stream modifications. Nine sites (five mainstem sites and four tributary sites) were sampled seasonally for one year. The Pedernales River is a typical Edwards Plateau stream with bedrock and cobble substrates, moderate current velocity, and it is well oxygenated, clear, and temperate. Upper reaches had swifter current velocities and coarse substrates with decreasing substrate sizes and current velocities downstream. A total of 52 families from 10 orders of aquatic insects were identified and dipterans and ephemeropterans dominated the assemblage (66.6%). Aquatic insect diversity ranged from 1.50 - 2.38 and fish diversity ranged from 1.00 - 2.09; upper reaches had higher number of habitat specialists whereas lower reaches had more habitat generalists. Thirty-five species of fish were identified and Cyprinidae was the most abundant family, comprising 68.1% of the assemblage. Endemic species to the Edwards Plateau comprised 7.4% of the fish assemblage whereas introduced species collectively represented 4.8%. Effects of wastewater effluent were apparent in Barons Creek and the mainstem Pedernales River directly downstream of its confluence with higher numbers of generalist and pollutant tolerant taxa, such as Chironomidae and red shiner Cyprinella lutrensis. Environmental parameters, season, and site explained 71.1% of the variability within the aquatic insect community and 64.2% of the variability within the fish assemblage. This region is considered a priority for conservation and the Pedernales River is a system under various degrees of degradation. Predictive models from these data help understand how communities shift with increased urbanization and how distributions of endemic taxa will be affected when overlapped with some of the fastest growing metropolitan areas in the country.



aquatic insects, fish communities, urbanization, streamflow, watershed management


Shattuck, Z. R. (2010). Spatiotemporal patterns of fish and aquatic insects in an increasingly urbanized watershed of Central Texas (Unpublished thesis). Texas State University-San Marcos, San Marcos, Texas.


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