In general, the cooler the stream the more likely it is to support a sport fishery. Streams maintained by groundwater discharge will have lower temperatures than those maintained primarily by surface runoff. Streams with healthy plant communities, including trees along their banks, will tend to have lower temperatures than streams that are open to sunlight.

Streams with consistently low levels of dissolved solids (salt, metals, and other toxins) offer better game fish habitat. Dissolved solids often increase in streams that are surrounded by high levels of development and impervious surfaces (roads, driveways, roofs). The dissolved solids are carried through runoff from precipitation, snowmelt, and erosion directly into the river.