Water Temps, What’s the big Deal?

Recently we have been asking a lot of anglers in the shop if they happen to carry a stream thermometer, and to our surprise we would say 90% of anglers out there are not equipped with one. If we had to rate our gear from most important on down, we would say our stream thermometers are right next to rods, reels, boots, waders, and flies. Let’s just say this piece of gear keeps our sanity on the river, and this is why. For one, it tells us what the fish might be doing even before the first cast, it tells us where to fish and when, it tells us why the fishing might be slow and why the fishing is so good at particular times. Here is an example of a fishing day in North Gate Canyon and why this piece of gear kept us on the fish. This particular day started cool and we were there early, the morning was crisp and the water felt cold on the legs through our waders. The forecast for the day was to be hot with minimal cloud cover so we knew the good fishing window would be mid-morning. In this situation one might think to start in the slower deeper pools and runs, then fish the faster more oxygenated riffles once the water warms up a little. We rigged our gear (deep nymph rigs) next to a nice slow deep pool that any angler would drool over and likely start in. After our rigs were set, next came a stream temp reading, 57 degrees, hmmmm, feels colder than that to us, checked it again, 57 degrees. Our next step was a change from deep nymph rigs to big attractor dry dropper rigs, the thermometer had changed our minds and where we would start on the river. Optimal feeding temps for trout range from around 52 to 58 degrees, and a reading of 65 or higher is very warm for trout, and it is best to let the fish rest if this is the case. On this particular morning a reading of 57 degrees told us trout were probably feeding heavily and were already awake and moving into the riffles in anticipation of a hot day. We bypassed the slow inviting deep pool and made our way up stream to a boulder field filled with endless runs and shallow riffles. These riffles were to be our target mid-day once it got hot, but 57 degrees meant one thing to us, fish the fast cool oxygenated water to start. Needless to say, fish were hooked within a few casts. We worked the boulder fields landing several nice trout and the sun only got hotter and stream temps were taken often, 57, 59, 61, then 63, the fishing started to slow down. This is where the stream thermometer will keep an angler’s sanity. If you don’t have one and didn’t know the water was creeping into the 60’s, one would be left fumbling over flies, tippet size, and hmmm, why did it slow down, it was so good 30 minutes ago. The reality is the fish are off the bite, and at this point it was a good time to sit and eat lunch instead of scratch our heads staring at a fly box. Now it was decision time, stay and fish, or go home and return for an evening hatch when the water has had time to cool. If there were no clouds then it would be an easy decision to return later as the water would only get hotter as the day went on, but on this day a big cloud was making its way in our direction. We cracked a PBR and decided to see what the clouds were going to do. We knew if we got cloud cover temps would drop and fishing might pick up again. Sure enough the clouds rolled in and we sat in anticipation taking stream temps once again, 63, 61, crack another PBR, 60, then 58. Our fishing window was back and we were able to work the same set of riffles again turning and landing several nice fish.  On this day you might say the stream thermometer was the most important piece of gear, it told us where to start and when, it told us when to stop, and it told us when to start again avoiding a dull fishing window which would send most anglers packing back up the trail. An important piece of gear and a must have in our minds? We think so….

Authored By: Tim Drummond (NPA Guide)