Spatiotemporal Patterns of Fish and Aquatic Insects in an Increasingly Urbanized Watershed of Central Texas
Date
2010-05
Authors
Shattuck, Zachary R.
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Abstract
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.
Description
Keywords
Aquatic insects, Fish communities, Urbanization, Streamflow, Watershed management
Citation
Shattuck, Z. R. (2010). <i>Spatiotemporal patterns of fish and aquatic insects in an increasingly urbanized watershed of Central Texas</i> (Unpublished thesis). Texas State University-San Marcos, San Marcos, Texas.