National Water-Quality Assessment (NAWQA) Project

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Effects of Urbanization on Stream Ecosystems

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Fish Communities

• A fish community is a group of fishes belonging to a number of different species that occur in the same section of stream and interact with each other. Fish community structure (the kinds of species and their abundances) is a useful indicator in water-quality assessments because it responds to and integrates the effects of environmental stressors over a longer period of time (year to multiple years) compared to benthic algae and invertebrates that have shorter life spans. Fish community structure is determined by the species present, their relative abundances, life-stages, patterns of growth and development, and their distributions in space and time. Human influences associated with increased urbanization, such as changes in stream water chemistry, flow, or physical habitat modifications, can alter fish community structure in a stream. In this study, fish communities were compared at sites along a gradient of urban intensity from low to high and were examined in relation to other physical, chemical, and biological factors.

What we measured:
• Fish community structure in a representative reach of stream that is at least 150 meters in length.

When we sampled:
• Fish collections were conducted once during low-flow conditions at each site.

Field collection protocols:
• Fish were collected using protocols described in Meador and others, 1993 for samples collected in 2000-2001 and Moulton and others, 2002 for collections in 2002 to present.
• A representative sample of the fish community is collected by sampling a stream reach using two complementary methods: electrofishing and seining. Electrofishing is conducted in two separate passes along the length of the study reach; followed by seining.
• Fish processing in the field includes species identification and measuring total length, weight, and anomalies. Unidentified fish are preserved for later identification in the lab.

Laboratory analyses:
• Fish that could not be identified in the field were retained for identification and enumeration in the laboratory (Walsh and Meador, 1998).

Quality assurance and control:
• Quality assurance and quality control of fish taxonomic data are described in Walsh and Meador, 1998.

What these data represent:
• Fish communities change in response to changes in stream chemistry and physical habitat. In urban and urbanizing areas these changes in fish communities can be used to determine how urbanization is affecting the physical, chemical, and biological conditions of streams.
• Changes in fish community structure in response to urbanization might include changes the number of species, the relative abundance of different species, abundance of functional groups (for example, feeding habits or tolerance to environmental stresses), abundance of life history stages (number of different age groups), and sizes of individual species.

Meador, M.R., Cuffney, T.F., and Gurtz, M.E., 1993, Methods for sampling fish communities as part of the National Water-Quality Assessment Program: U.S. Geological Survey, Open-File Report 93-104, Raleigh, 40 p. []

Moulton, S.R. II, Kennen, J.G., Goldstein, R.M., and Hambrook, J.A., 2002, Revised protocols for sampling algae, invertebrate, and fish communities as part of the National Water-Quality Assessment Program: U.S. Geological Survey Open-File Report 02-150, 75 p. []

Walsh, S.J., and Meador, M.R., 1998, Guidelines for quality assurance and quality control of fish taxonomic data collected as part of the National Water-Quality Assessment Program: U.S. Geological Survey, Water-Resources Investigations Report 98-4239, 33 p. []

Photos of fish sampling in Raleigh, North Carolina Study Area

Video clips of fish sampling in Raleigh, North Carolina Study Area


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