Here is why you need to monitor the water flow gages (I do not know why they spell it that way) for temperature if you go trout fishing. You will be unlikely to catch anything when the water is below 40 degrees! Also, as rivers and streams warm in the summer, you need to switch to smallmouth bass since trout may die if stressed from being caught and released in warm water.
And… this is important! Do not practice catch and release with stocked trout! Stocking programs occur during the spring and fall when the water is cold enough for trout to survive. But, when those same streams warm up in the early summer, the trout die! So, instead of wasting them, keep them and have a good meal!
Here’s a quick-reference chart summarizing trout behavior in response to water temperature:
Trout Temperature Behavior Chart (°F)
| Temperature Range | Trout Behavior | Feeding Activity | Migration Likelihood |
| 32–39°F | Sluggish, low metabolism | Minimal to none | Unlikely (already in winter habitat) |
| 40–45°F | Conserving energy | Slow, selective feeding | No migration unless oxygen drops |
| 46–55°F | Active, optimal metabolism | Moderate to strong | Stable, no migration |
| 56–65°F | Peak activity and growth | Strong feeding | No migration |
| 66–68°F | Onset of thermal stress | Reduced feeding | Begin seeking cooler refuges |
| 69–74°F | High stress zone | Sporadic feeding | Active migration to coldwater sources |
| 75°F+ | Lethal range for prolonged exposure | Feeding stops | Urgent migration or mortality risk |
