Regional, watershed, and site-specific environmental influences on fish assemblage structure and function in western Lake Superior tributaries

Abstract

The relative importance of regional, watershed, and in-stream environmental factors on fish assemblage structure and function was investigated in western Lake Superior tributaries. We selected 48 second- and third-order watersheds from two hydrogeomorphic regions to examine fish assemblage response to differences in forest fragmentation, watershed storage, and a number of other watershed, riparian, and in-stream habitat conditions. Although a variety of regional, fragmentation, and storage-related factors had significant influences on the fish assemblages, water temperature appeared to be the single most important environmental factor. We found lower water temperatures and trout–sculpin assemblages at lower fragmentation sites and higher temperatures and minnow–sucker–darter assemblages as storage increased. Factors related to riparian shading and flow separated brook trout streams from brown trout (Salmo trutta) – rainbow trout (Oncorhynchus mykiss) streams. Functionally, fish assemblages at lower fragmentation sites were dominated by cold-water fishes that had low silt tolerance and preferred moderate current speeds, while fishes with higher silt tolerances, warmer temperature preferences, and weaker sustained swimming capabilities were most common at higher storage sites. Our results suggest that site-specific environmental conditions are highly dependent on regional- and watershed-scale characters and that a combination of these factors operates in concert to influence the structure and function of stream fish assemblages.

Longitudinal patterns of fish assemblages in small unregulated subbasins: evaluating reach- and watershed-scale parameters

“…Environmental relationships with fish assemblages vary spatially from localized in-stream habitat structure (Gorman & Karr, 1978), landscape-level parameters (Wang et al, 2003), to broad-scale regional factors (Brazner et al, 2005). The indirect gradient and subsequent site score correlation analyses generated in this study showed that within all four subbasins that natural environmental gradients at the reach scale were more influential than watershed-scale land-use features on fish assemblages.…”

A Reduced Parameter Stream Temperature Model (RPSTM) for basin-wide simulations

“…More than 85% of stream water volume in the tributaries of the Muskegon River is derived from groundwater (Boutt et al, 2001;Pijanowski et al, 2007). Thus groundwater fed tributaries are important in sustaining the cold-and cool-water fish species (Clapp et al, 1990;Wiley et al, 1997;Brazner et al, 2005;Creque et al, 2005), which are common in much of the river system. Nonetheless, there is concern that a number of important fishes may become susceptible to thermal stresses (O'Neal, 1997;DePhilip et al, 2005;Larson et al, 2013) resulting from land use changes (e.g., urban sprawl) (Pijanowski et al, 2006(Pijanowski et al, , 2007, climate change , and hydropower production (Horne et al, 2004).…”

Do existing ecological classifications characterize the spatial variability of stream temperatures in the Great Lakes Basin, Ontario?

“…As it was the only classification developed specifically for streams, its third-place ranking is interesting. The variables that have been included in the AEC do influence stream temperatures and are linked to stream biota (Wang et al, 2003;Brazner et al, 2005). However, the weakness of the AEC is that it does not include climatic variables that also affect stream temperature.…”