Spring has arrived in Montana and fishing conditions are changing rapidly. This is a very exciting and dynamic time of year to target Montana waters. Conditions can change by the day and even by the hour so paying close attention to weather and flows is a huge part of the late spring fishing game. What happened yesterday is not necessarily a good indication of what will happen tomorrow so be very cautious about running to a fishery because your buddy had a great day there two days ago or because a fishing report talked up how epic the fishing has been. Remember that by nature fishing reports are 100% stale information. This report will focus on some generalities about late spring fishing but will also focus on some tools that you can use for predicting when to be at the right time to catch some windows of mind blowing fishing that often arise this time of year – often in narrow windows. Do not be discouraged by the fact that some waters are high and muddy, the waters that are fishable are spectacular right now and this is one of our absolute favorite times to target local waters. There are few out of state anglers and often you can have incredible fishing with light pressure. The only fisheries that you will see a good number of other anglers on right now are the tailwaters.
As temperatures warm the mountain snowpack melts and brings up water levels on all fisheries except spring creeks and stillwaters. In general, freestone fisheries are a tough option right now. Freestone rivers and streams are those that rely heavily on overland flow from rain and snowmelt. These streams and rivers (Think the Gallatin and Yellowstone) become high and dirty with sediment during late spring run off and are not fishable most of the time (but not all of the time! – see notes below). Spring creeks are fed by groundwater and are completely unaffected by run off. Some rivers are also fed from reservoirs that trap sediment. These tailwaters (Bighorn, Missouri, Madison etc) do increase in flows during spring run off but they retain good water clarity and often great fishing. Stillwater reservoirs, ponds and lakes are also a very good option this time of year.
There are no shortage of insects available to trout on our local waters this time of year. The most important hatches are the spring baetis mayflies, March Brown mayflies and the Mothers Day caddis. Hatches may or may not bring trout to the surface but it is important to know that the trout are looking for these bugs, even if they are eating subsurface. Don’t go anywhere in the late spring without imitations of nymphs, emergers and dries of the aforementioned species. There are a variety of different patterns that are effective and most work just fine. Don’t forget about a large size 12 hares ear when you see March Browns – they don’t always hatch in abundance but trout love them. When fish are feeding on the surface, also try hanging an emerger just a foot or so behind your dry. Watch rise forms carefully. If trout look like the are porpoising they are probably taking emergers and not duns/adults.
The safe bets right now are the waters that are protected by run off. These include tailwaters below reservoirs, spring creeks and still waters. The good news is that these three categories of fisheries are lights out right now and occur in abundance across Southwest Montana. Spring creeks have consistent baetis hatches and sometimes caddis on a daily basis and are a very safe bet for dry fly fishing. The fish are still fresh and haven’t seen a lot of artificials yet so catch rates are often high. Tailwaters are also coming alive right now as water temps rise and the trout put on their feedbags. Dry fly fishing is variable and depends on flows and if they are bumping the dam releases or not. Nymph fishing is predictably good. If flows are on the rise fishing closer to the dam is often better because moss can often get dislodged and if you are too far downstream it can foul hooks. Stillwaters are also a great option and catch rates can be very high slow stripping streamers. Early Callibaetis mayflies can also produce good dry fly action on some waters.
Wild card Options
Many anglers completely right off freestone fisheries from mid May until waters clear in early summer. This is huge mistake! Savvy flyfishers that tune a watchful towards hydrographs and weather patterns are often rewarded with spectacular days without another angler in sight. What you want to watch for is a cool down in the weather forecast. If a cooler weather pattern that sets in it can suspend snow melt and rivers can quickly respond. Every fishery is different – some of the larger ones like the Yellowstone take a big cold snap with a longer duration to produce fishable waters but smaller rivers can clean up and go on the drop even after a single day of the right weather. Remember that the water does not need to be clear – you just need as little as six inches of visibility to have great fishing. If the hydrograph shows the river is on the drop and is missing the “yo-yo” pattern of rising water from daytime sun followed by falling water from the evening then it is a good bet it may be fishable. Don’t expect dry flies but streamers and big ugly nymphs can be deadly. Target the soft water where fish are staked up like inside corners and seams behind large rocks. Sometimes these windows only last one or two days so you need to respond quickly when the conditions warrant.