Relation of Fish Communities to Physical and Chemical Variables at Nine Stream
Sites in the Platte River Basin
By Robert B. Swanson and Steven A. Frenzel
ABSTRACT:
Species composition of fish communities was related to selected physical and
chemical variables at nine sites in the Platte River basin from North Platte,
Nebraska downstream to the confluence with the Missouri River near Omaha,
Nebraska. The multivariate data included abundances for 36 fish species,
characteristics of the nine drainages, site-specific habitat and water-quality
characteristics measured during the 1993 water year. Land-use variables were
calculated for the entire drainage area at sites draining less than 4,000
km2, and for the lower 4,000 km2 of larger
drainages. Canonical correspondence analysis was used to relate environmental
characteristics to species data. This method restricts the number of
environmental variables to be less than the number of samples. To reduce the
number of variables a correlation matrix of 37 variables was examined. Many
variables such as concentrations of four herbicides, nutrients, and dissolved
organic carbon were highly correlated with each other and with the percentage
of the drainage area in cropland. Six variables selected for analysis were:
percentage of drainage area in cropland, maximum water temperature, minimum
suspended sediment concentration, channel slope, time since a flow of 99
percent exceedance, and the ratio of stream width to depth. These variables
explained 64 percent of the variability in species data. Ordination of the
fish community data showed that larger river sites which typically had more
fish species than smaller sites were grouped together. Two sites draining
areas with more than 90 percent cropland were grouped together. Another
drainage dominated by cropland was isolated in the ordination. This site had
the fewest fish species (4) and lowest total abundance (43). A site in the
Nebraska Sandhills, predominantly herbaceous rangeland, also was isolated in
the ordination.
CITATION:
Swanson, Robert B., and Frenzel, Steven A., 1994, Relation of fish communities
to physical and chemical variables at nine stream sites in the Platte River
basin, [abs.], in Sorenson, Stephen K., ed., 1994, Proceedings abstracts
American Water Resources Association's symposium on the National Water-Quality
Assessment Program--November 7-9, 1994, Chicago, Illinois: U.S. Geological Survey
Open-File Report 94-397, p. 19.