Riparian Shading and Groundwater Enhance Growth Potential for Smallmouth Bass in Ozark Streams

Abstract

Abstract. Moderation of stream temperatures by riparian shading and groundwater are known to promote growth and survival of salmonid fishes, but effects of riparian shade and groundwater on to be growth of warmwater stream fishes are poorly understood or assumed to be negligible. We used stream temperature models to relate shading from riparian vegetation and groundwater inflow to summer water temperatures in Missouri Ozark streams and evaluated effects of summer water temperatures on smallmouth bass, Micropterus dolomieu, growth using a bioenergetics model. Bioenergetics model simulations revealed that adult smallmouth bass in non-spring-fed streams have lower growth potential during summer than fish in spring-fed streams, are subject to mass loss when stream temperatures exceed 278C, and will likely exhibit greater interannual variation in growth during summer if all growth-influencing factors, other than temperature, are identical between the two stream types. Temperature models indicated that increased riparian shading will expand the longitudinal extent of thermal habitat capable of supporting adult smallmouth bass growth in spring-fed stream reaches when mean daily air temperatures exceed 278C. Optimum growth temperature (228C) will be present only in spring-fed streams under these conditions. Potential for increasing shade through riparian restoration is greatest for streams ,5 m wide and along north-south reaches of larger streams. However, temperature models also indicated that restoring riparian shading to maximum levels throughout a watershed would increase the total stream mileage capable of supporting positive growth of adult smallmouth bass by only 1-6% when air temperatures are at or near average summer maxima; increases in suitable thermal habitat would be greatest in watersheds with higher spring densities. Riparian management for maintenance or restoration of the thermal habitat of adult smallmouth bass during summer should be focused in areas strongly influenced by groundwater. Restoring riparian shading along spring-fed warmwater streams will likely benefit adult smallmouth bass growth and may ultimately influence population sizes.

Mercury bioaccumulation and biomagnification in Ozark stream ecosystems

“…The mining-derived sulfates originating from Blue Spring may also affect methylation rates, as may stream temperature. The latter may also influence Hg concentrations in fish through effects on feeding and growth rates (e.g., Norstrom et al, 1976;Whitledge et al, 2006;Ward et al, 2009).…”

“…Mercury concentrations (as MeHg) tend to increase with age and body size in upper trophic level fishes (Wiener et al, 2003(Wiener et al, , 2006McIntyre and Beauchamp, 2007), but size-concentration relations have not been evident in Ozark smallmouth . These relations can also be obscured by growth dilution (e.g., Ward et al, 2009), and growth rates can be influenced by the temperature stability afforded by springs (Whitledge et al, 2006). HgT concentrations also tend to be lower in smallmouth from streams that drain historical lead-zinc mining areas than elsewhere in southern Missouri (e.g., .…”

The influence of groundwater withdrawal and land use changes on brook charr (Salvelinus fontinalis) thermal habitat in two coldwater tributaries in Michigan, U.S.A.

“…Stream shading percentages were estimated through on-site evaluation. Components of SSTEMP, which aptly model individual stream reaches, and the more detailed SNTEMP, which models a complex network of stream reaches, have been used to evaluate the effect of altered flow regimes, stream widths, and riparian shading on water temperatures in a Colorado trout (Oncorhynchus mykiss and Salmo trutta) stream (Bartholow, 1991), evaluate the importance of groundwater and riparian shading on adequate bass (Micropterus dolomieu) habitat in Ozark streams (Whitledge et al, 2006), and determine the influence of stream shading in maintaining summer temperatures in a brook trout stream (Pajak, 1992). Additionally, Gaffield et al (2005) used an adapted version of SNTEMP, to illustrate the overall importance of groundwater and riparian shading as controls to summer temperature in small Midwestern streams while emphasizing the significance of temperature models in facilitating watershed management decisions.…”

“…Human activities which alter land cover within a watershed therefore have the ability to impact the thermal regime of stream ecosystems for brook charr (Dunne & Leopold, 1978;Bartholic et al, 1983;Wang et al, 2003;Gaffield et al, 2005;Wang et al, 2006;Whitledge et al, 2006). Under natural conditions, the groundwater system is constantly discharging (outflow to lakes, streams, and wetlands) and recharging (inflow from precipitation, loss to surface water bodies) to maintain equilibrium; however, this natural equilibrium changes when groundwater is withdrawn from the aquifer or land cover alterations reduce recharge rates to the groundwater aquifer.…”

The influence of riparian woodland on stream temperatures: implications for the performance of juvenile salmonids

“…Macdonald et al, 2003). In some cases the effects of variable harvesting practices have also been evaluated Gomi et al, 2006) and recent efforts have attempted to model observed differences in the spatial and temporal distribution of temperatures using process-based models (Rutherford et al, 1997;Chen et al, 1998a;Rutherford et al, 2004;Gomi et al, 2006;Whitledge et al, 2006;Cox and Bolte, 2007;Westhoff et al, 2007) with the aim of predicting the effects of future changes in land use (Rutherford et al, 1997;Chen et al, 1998b;Whitledge et al, 2006).…”