Although using Geographic Information Systems (GIS) has become common in ecology, few river stud- ies incorporate this technology into examining habitat variables and use of habitat by individual fishes. Our goal was to demonstrate these GIS techniques and to test for the ability to predict fish and habitat relationships using the same data in a multivariate analysis. We collected channel bathymetry, water velocity, and streambed composition using an Acoustic Doppler Current Profiler (ADCP) deployed from a USGS boat and interfaced with a Differential Global Positioning System (DGPS) receiver, for a 10-km study reach of the Wabash River. Individual fishes were collected the following week and assigned spatial coordinates for latitude and longitude. We tested for the ability of a multi- variate technique to explain fish assemblage variation using environmental variables collected in a GIS context. We tested at which of three resolutions the environmental variables explained the highest proportion of fish assemblage variation. For this 10-km reach of the Wabash River, fish assemblages were best explained at a 10 by 10 m resolution with water velocity, water depth, river location, woody debris, and substrate composition. At a lower resolution (30 by 30 m) the same habitat variables provided similar but lower explanation of variation. However, at the highest resolution of 4 by 4 m, environmental variables provided relatively little explanation of fish assemblage structure. We suggest and recommend additional applications of a GIS approach to test temporal and spatial hypotheses of stream fish assemblage structure.

1. The use of trait-based approaches to examine the ecology of stream fish assemblages is increasing. However, selection of traits that will be useful in testing spatial or temporal hypotheses about ecological organisation is currently limited by availability of data, rather than empirical evaluation. 2. We analysed two data sets of stream fish assemblages to compare taxonomy and trait-based approaches. The Wabash River temporal data set is based on 25 years of boat electrofishing collections over a 230-km river distance. The Indiana Department of Environmental Management data set of stream collections in the state of Indiana was selected to represent a spatial database. We compared several trait-based approaches: reproductive guilds, life history variables, biomonitoring metrics, ecosystem-based functional guilds and feeding and ecosystem interaction guilds. 3. Analyses of fish assemblages that are designed to detect how environmental variation structures fish assemblages can expect similar results using taxonomic or trait-based approaches. Results of trait-based approaches will vary according to the spatial extent of the region and the number of unique entities of trait groups for a given data set. However, taxonomic analyses accounted for more variation than any trait-based analyses.

Stream channelization results in modifications to the natural meandering of stream channels. Channelized streams experience higher rates of drying in late summer and early fall because of efficient water movement and higher water temperatures. Approximately 70% of east-central Indiana landuse is rowcrop agriculture with widespread Stream channelization. We sampled fishes and invertebrates at 14 sites in seven headwater streams in the Buck Creek watershed. We defined streams that dry in late summer and early fall as seasonal, and those that maintain flow throughout the year as perennial streams. Our predictions were that alterations to the natural channel structure, which change the seasonal drying patterns of the streams, would also cause changes in fish and invertebrate assemblages. Detrended Correspondence Analyses (DCA) of fish and invertebrate assemblages produced significant correlations for resulting axes with habitat and water quality variables. No significant differences in fish and invertebrate assemblages were found in our comparisons of seasonal vs. perennial streams.

We examined abundances of fishes by ecological categories for variation with time (years) and longitudinal river distance (km) in the Wabash River, a large US Midwestern river. An ordination resulted in significant correlations with time for an axis that represented increases in surface-feeding invertivores and species that prefer sand substrates. We found increased abundances of planktivores and species with high tolerance to silt in downstream river sites. We found significant changes in abundance for the majority of ecological categories in comparisons of upstream–downstream locations. There was a general decrease in abundances of taxa in ecological categories that tend to inhabit upstream reaches: species that prefer rubble substrates, inhabit fast, and moderate current velocity habitats, and that have low silt tolerance with time. These abundance changes suggest that the upstream river experienced increased sedimentation during 1974–1998. The use of ecological categories provided information for likely habitat changes, such as increased sedimentation, that were not apparent in previous taxonomic analyses. We suggest that combinations of anthropogenic impacts including hydrologic alterations and agricultural activities in the Wabash River resulted in ecosystem changes and subsequent changes in abundance of fishes by ecological categories.

We collected aquatic gastropods at 137 sites in lakes and streams of Indiana and tested for patterns of assem- blages with environmental variables. The survey resulted in 32 species with a mean of 2.8 species at each site, and a mean abundance at each site of 144 individuals. Nonmetric multidimensional scaling (NMS) multivariate analyses resulted in watershed drainage area, water conductivity, substrate category frequency, and dissolved oxygen as significant correlates of gastropod assemblage structure. Gastropod assemblages of lakes were not significantly different than assemblages of streams in the ordination. Prosobranch taxa occurred in higher abundances than pulmonate taxa at sites with lower con- ductivity in larger watersheds. There were no pairs of gastropod species that tended to co-occur more frequently than ran- dom. Our analyses resulted in local environmental variables providing explanation of aquatic gastropod assemblage struc- ture.

We surveyed Indiana collections of freshwater gastropods from 220 museum collection lots and found 39 species inhabiting Indiana historically. Collection dates of museum material ranged from 1900 to 2006, with a median date of 1986. We collected 17,593 gastropods at 123 sites, including 86 sites where museum material was previously collected. Our surveys were combined with recent literature surveys and indicate a total of 36 species are currently present in Indiana. The Indiana fauna is composed of three species that are apparently secure globally, and 36 species that are widespread, abundant, and globally secure, including two exotics. However, three species are locally extinct and many others are locally imperiled or vulnerable. The majority of freshwater gastropod taxa in Indiana are of local conservation concern. The causes of local gastropod extinctions are unknown but likely include agricultural impacts, hydrologic alterations from reservoirs, and pollution. We recommend thorough inventory, recognition, and protection of the aquatic gastropods in Indiana.