Fish community relationships with hydrological and landscape characteristics in Iowa rivers and streams
Date
1998
Authors
Madejczyk, Jeffrey Charles
Major Professor
Advisor
Pierce, Clay L.
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Abstract
Stream fish communities are known to be affected by hydrological, physical-chemical, and landscape-level characteristics. Relationships of these characteristics with fish communities in Iowa rivers and streams were examined. Iowa's landscape is currently dominated by agriculture, with little of the native prairie-marsh-pothole complex remaining. Extensive row cropping, stream-side grazing, channelization, drainage tiling, and introduction of exotic species have altered the streams and their fish communities. Analysis of Iowa land use revealed few substantive differences at the landform or catchment-wide level. More pronounced land use differences were seen in channel buffers adjacent to streams. Twelve measures of hydrological variability and predictability were used to characterize flow in Iowa streams.
Streams in Iowa were found, on average, to be more variable, less predictable and relatively harsh when compared to an inventory of streams across the USA. No evidence of aggregation of fish communities by landforms or catchments was found. Several weak relationships between various species or functional groupings of the fish community with environmental variables were seen. Abundance of channel catfish and top carnivores were positively correlated with stream size. Top carnivores and gamefish were positively correlated with forests and wetlands near the stream channel. Although weak, these relationships confirm similar relationships in previous studies. Cluster analysis was used to group streams based on similarities in functional attributes of the fish community.
Canonical discriminant analysis successfully discriminated among these groups using, hydrological measures of variability and predictability, suggesting a relationship of fish community organization and hydrological regime. Overall, results suggest that the climate and uniformly highly altered landscape of Iowa results in relatively harsh hydrological conditions for stream fish. This, along with the resulting landscape homogeneity apparently results in fish communities lacking many of the strong structural patterns and environmental relationships evident in studies conducted in more pristine or heterogeneous settings.
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