Idaho Rivers


What to Expect in December

Note: This What-To-Expect is from Westfly's Legacy pages and may not accurately reflect the current fishing at this venue

In early winter, fly anglers need to adapt their tactics to the conditions. First, understand the needs of trout. Since trout are cold-blooded, their metabolism slows as the water cools. That means they don't need as much to eat, and they will not waste any energy pursuing what little food they need. They will be most active on warmer days, at the warmest time of each day--usually from 11:00 a.m. to 2:00 p.m. Trout will be found in slower, deeper water than they occupied in summer.

Second, understand what food is available to trout in winter. The big hatches are over. From now until spring the primary aquatic insects that trout will see are blue-winged olives and midges. Both larval and adult forms of these insects will be present. But bugs aren't the only things on the menu. Trout will also eat drifting roe from spawning brown trout, brook trout, and whitefish. Larger trout will eat baitfish, as well.

Most importantly, pick the right flies, the right days, and the right places, as described below.

For Blue-winged olive: Pheasant Tails or gold-ribbed Hares Ears for nymphs; CDC Baetis or Baetis Cripple emergers; Parachute Baetis or Sparkle Duns to match duns; and Rusty Spinners to match the final stage (usually not important in winter, but be prepared). All flies in size 18-22, but mostly in size 20-22. Nymphs are productive most of the active part of the day(11:00 to 2:00, with maybe an hour on either side of those times if the day is warm). Blue-winged olives are most likely to hatch on cloudy days. In the Rockies, they are strongest in the first half of November or until really cold weather settles in. They'll be back again in March and April. Look for feeding fish in backeddies and slow runs. Nymphs should be presented right on the bottom.

For midge imitations: Brassies or Copper Johns to imitate the larvae; Sprout Midges or Griffiths Gnats if trout are taking adults on the top. Carry these in sizes 18-22. The larval patterns are the most effective. In early November, you might find trout feeding just subsurface. Once it turns really cold, however, trout will hunker on the bottom and won't budge unless there's a pretty good hatch that creates a surface-feeding opportunity. So once the weather becomes frigid, you'll need to drift those larval patterns on the bottom

For roe imitations: peach, pink, and orange are the best colors. Dead-drift them on the bottom.

To imitate baitfish: Matukas, Egg Sucking Leeches, Muddlers, Clouser Minnows, sculpin imitations, etc. Usually these work best when fished from a boat because you can cast to the bank, but the boat is not essential. A sink-tip line is an aid because you need to get the fly near the bottom. Cast, let the fly sink, and retrieve slowly. This is not exciting fishing, and you'll be lucky to pick up a fish or two a day. But each fish could a brown trout that tops five pounds.

And of course, standard nymphs. A frequent winter tactic is to cast a size 8-10 Prince with a Brassie, Copper John, or Pheasant Tail on a trailing leader tied to the Prince's hook bend.

While fly choice is important, it's even more important to pick the right day. Anytime it starts to warm up, you can think about hitting the water.

Always take extra clothes. If you execute a full-immersion hat-floater when it's near freezing and the wind is blowing25 mph, you are in big trouble and need to get into dry, warm clothes quickly.

And pick the right place. Some streams are in cold places. That's usually not where you want to go. The best choices have relatively warmer weather. Tailwater fisheries and spring creeks are productive because the water is usually warmer than in other streams. Most fish will be found near the edges and in deeper pools, backeddies, slow runs, and pools below riffles.


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