Geomorphology and fish assemblages in a Piedmont river basin, U.S.A.

Abstract

Summary 1. We investigated linkages between fishes and fluvial geomorphology in 31 wadeable streams in the Etowah River basin in northern Georgia, U.S.A. Streams were stratified into three catchment sizes of approximately 15, 50 and 100 km2, and fishes and geomorphology were sampled at the reach scale (i.e. 20–40 times stream width). 2. Non‐metric multidimensional scaling (NMDS) identified 85% of the among‐site variation in fish assemblage structure and identified strong patterns in species composition across sites. Assemblages shifted from domination by centrarchids, and other pool species that spawn in fine sediments and have generalised food preferences, to darter‐cyprinid‐redhorse sucker complexes that inhabit riffles and runs, feed primarily on invertebrates, and spawn on coarser stream beds. 3. Richness and density were correlated with basin area, a measure of stream size, but species composition was best predicted (i.e. |r| between 0.60–0.82) by reach‐level geomorphic variables (stream slope, bed texture, bed mobility and tractive force) that were unrelated to stream size. Stream slope was the dominant factor controlling stream habitat. Low slope streams had smaller bed particles, more fines in riffles, lower tractive force and greater bed mobility compared with high slope streams. 4. Our results contrast with the ‘River Continuum Concept’ which argues that stream assemblages vary predictably along stream size gradients. Our findings support the ‘Process Domains Concept’, which argues that local‐scale geomorphic processes determine the stream habitat and disturbance regimes that influence stream communities.

Longitudinal structure of fish assemblages in a minimally disrupted stream

“…Schlosser 1982;Vlach et al 2005). In contrast, stream slope as the primary factor strongly influences the species composition (Walters et al 2003) or as a secondary factor (Lyons 1996;Maret et al 1997). In a relatively undisturbed stream in central Europe a continuum in the physical structure of habitat, patches ranging from riffles to pools were characterised (Erős et al 2003(Erős et al , 2005b.…”

Geospatial Modeling of River Systems

“…Geomorphology has often been recognized as an important factor in defining biological [10,11] and ecological characteristics of rivers [12,13] and ultimately the shaping of aquatic habitat [13,14]. The term habitat refers to a location or environment where an organism is most likely to be found and can include physical, chemical and biological characteristics that allow the organism to achieve various life history requirements, such as spawning, feeding, and overwintering.…”

The role of topographic variability in river channel classification

“…NMDS is common in ecological studies, including those identifying differences in biological communities based on geomorphic variables (e.g., Virtanen et al, 2010;Walters et al, 2003;) and is increasingly included in dedicated geomorphic studies (e.g., Jaeger, 2015; Merriam et al, 2011;Sutfin et al, 2014;Varanka et al, 2014;). Histograms of each geomorphic attribute were also used to evaluate the density distributions of attribute values across the survey reaches and lend insight into the multivariate clustering structure.…”