The flow and temperature in these streams is more variable. Freestone streams do not have as much dissolved calcium as the limestone streams and are vulnerable to changes in pH. These streams also tend to flow off ridges and through areas with hilly topography, making the riparian zones less likely to be cultivated. Although freestone streams do not have the large springs discharging to the stream, the absence of alterations to the riparian habitat is favorable for fish communities. The habitat characteristics that proved most influential in defining fish communities in the seven long-term monitoring basins were mean channel width, mean water temperature, mean canopy angle, and suspended sediment. These four variables combined accounted for about 79 percent of the variation in the stream habitat-species relation.
Fish are sensitive to water temperature.
Streams with moderate water temperatures have species found in both the cooler and warmer streams. Canopy angle and channel width, which affect water temperature, influence the fish species that are able to inhabit a stream. Canopy angle determines the amount of sunlight that reaches the stream surface. Steep, high banks with little vegetative cover have a greater chance of erosion during storms than lower banks with more vegetation. Banks consisting of finer sediment are more erodible than banks that consist of cobbles and boulders.