Winter Fly Fishing for Trout

Water in the 30s and 40s, a short afternoon, and flies the size of a comma.

From the book Fly Fishing for Nerds — $9.74 →

The 50s, the olives, and the weeks before brown trout are on the gravel belong on the fall guide. This page starts when the thermometer in the run reads the 30s or the 40s.

Use the same loop as the observe page: observe, then hypothesize, then test. The reading, the hour, and one look at the ice are the observation. One sentence about the lane is the hypothesis. A handful of slow drifts is the test.

1. What changes in the 30s and 40s

Measure the river before you open the fly box. The water-temperature guide is how to take the reading. The stop near 68°F lives on that page.

For trout raised as a crop, SRAC Publication 223 puts the minimum temperature for growth at about 38°F, and the optimum at 55–65°F. NC State Extension says to cut feeding back when the water is below 45°F. A reading in the 30s or the low 40s is at or under that 45°F line, and it can sit on the 38°F floor. The fish are still in the river. They are not in the band where an all-day feed is the fair hypothesis. The time-of-day guide calls about 45°F and below the cold band: a short session in the warmest part of the day.

Idaho Fish and Game says winter fish move slower, hatches are sparse, and both the flies and the tippet go smaller. Their example is stepping down from 4X to 5X, because winter water is often lower and clearer and a trout can see a clumsy tippet. The tippet guide is what the X number measures. Change the tippet because the fly changed, then repeat the same drift.

2. A short window in the middle of the day

Idaho Fish and Game says that on most winter fisheries the fish are not feeding hard until mid- to late morning. On a sunny day they are most active in mid-afternoon. On a cloudy day the afternoon runs longer. Skip the dark start. Two hours inside that window is a complete test. A dawn start, in water near freezing, tests an hour the fish are not using.

The time-of-day guide already files winter as that short session. Take the temperature when you start and again before you quit. If the second reading has dropped, you are past the window. A gray afternoon can still be the midge hour. If you see the bugs, fish them. If the surface stays quiet, stay with the nymph.

3. Slow water and the soft side of a seam

Idaho Fish and Game tells you to seek slow, deep water, where trout hold while spending as little energy as they can. Look for slow pockets and pools where the water is barely flowing. Iowa DNR puts the same idea on the edge: trout do not randomly spend energy, and you find them along the edge of the current, near cover.

That edge is the soft side of a seam, the deep bucket, the inside of a bend where the surface is slower. The fast riffle you fished in June is a poor first test when the water is in the 30s. The reading-water guide is the walk. A handful of drifts that actually track is the test. A drift that races is not a result.

Read today's discharge with the river-flow guide before you drive. Ice can throw a gauge's rating. If the graph and the river in front of you disagree, believe the river.

4. Tailwaters and spring creeks

Not every river is in the 30s on the same afternoon. Minnesota DNR says the best trout streams there are fed by springs that average less than 50°F, which is why those creeks stay cold in summer. The same groundwater is why a spring creek can stay open when a runoff creek ices over. Virginia DWR, writing about the South Fork of the Holston, says limestone springs keep that river's temperature more even than the creeks around it: the coldest water in summer and the warmest in winter. Afternoon olives and midges are the hatch they name on that water. Your spring creek is a different rock. The thermometer is the check.

A tailwater is the other place to measure. USGS describes a winter lake whose surface gets colder than the deeper water, which holds a steadier temperature through the year and is then warmer than the surface. A dam that releases from low in the reservoir is drawing that deeper water, not the skin of ice. In summer that release is the cold one. In winter it can be the water that has not matched the air. Idaho Fish and Game points at two of its own, the South Fork of the Boise below Anderson Ranch Dam and the Snake below American Falls, as winter water a dam release keeps fishable. Those are Idaho rivers. A freestone above your reservoir can be locked while the first mile below the dam is open. If it is open, fish it. If the reading is still in the 30s, you are still on this page.

5. Midges, small nymphs, and a slow drift

Idaho Fish and Game says dead drifting is the winter cast, because trout will not chase a fly in cold water. Let the slow current carry the fly. If you see dimples, the food is likely tiny midges or mayflies, and a small emerger is the surface test. A dry-fly hour is the exception. If the surface is quiet, do not start there.

The North Carolina Wildlife Resources Commission hatch chart lists midges from January through March, in the afternoon, in sizes 18–24: a gray or olive midge, a Griffith's Gnat, or a Renegade. The same chart puts blue-winged olives in February and March, early afternoons on warm days, size 18. That calendar is North Carolina's. The bugs over your run are the check. Catch one if you can. The size comes from the insect in your hand.

Nothing on top is the usual hour. That opening is the no-hatch guide: one nymph, one depth, one lane. The indicator guide is where the float goes when you cannot see the take. Change depth before you change flies. Let the drift finish.

Minnesota DNR, in Minnesota Conservation Volunteer, tells winter fly anglers to carry midges, nymphs, emergers, and streamers, and says midwinter fishing is slower than the rest of the year. Slower is the point of the test. It is not a reason to add a second fly in the same cast.

A size 20 midge usually wants 6X, a step past Idaho's 4X-to-5X example. Tie the tippet the fly asks for, then repeat the drift you already ran. Two changes in one cast leave you unable to say which one mattered.

6. Ice in the guides, and a slip

Idaho Fish and Game names frozen guides as part of the day. Minnesota DNR's winter story has the angler punching ice out of the eyelets. A guide full of ice hinges the cast, and a hinged cast is not a drift you can score. Wipe the guides. Put a thin coat of de-icer paste on the guides and on the line before the first cast, and again when the ice comes back. If the paste cannot keep the line moving, the test is over. Fingerless wool gloves leave the fingertips free to tie, and they cover the rest of the hand while you do it.

Water in the 30s is the day for breathable chest waders, not wet shoes. The Simms Tributary stockingfoot waders are that pair: the foot goes under the boot, and the chest keeps this cold water out for the short midday session.

Cold water is the other clock. The U.S. Coast Guard's boater guide says sudden immersion can bring a gasp and uncontrolled breathing, and that this cold shock passes in about a minute. In the next 10 minutes you can lose the useful use of your fingers, arms, and legs. Hypothermia, an abnormal drop in body temperature, can follow, and loss of consciousness may come in as little as an hour, depending on the water. The same guide corrects a wading myth: heavy clothes and waders do not make you sink at once. Air in the clothes floats you, and bending your knees traps more air in the waders. Thrashing spends that air, and it spends you.

If you go in over the top of the waders, the fishing is finished. Bend your knees, get to the bank, get dry, and get warm. Do not try one more drift in wet fleece. Shelf ice along the edge is not a step. Minnesota DNR's trip note says to tell someone where you are going, and to have a plan if something goes wrong. Footing and that plan are the first item on the bank checklist.

7. The eggs are still in the gravel

The spawn was the fall page. The eggs are a winter fact. Iowa DNR says not to disturb active trout redds, the patches of cleaned gravel, from late fall through the winter. Brown trout and brook trout put their eggs in those patches, and the eggs stay there until they hatch in late winter or early spring. Avoid stepping on or near one. NOAA Fisheries says not to fish or wade near a redd, because a step on it or next to it can kill eggs. Pennsylvania Fish and Boat says brook and brown trout eggs need water between 35 and 55°F to survive. That range is why the pale gravel stays closed to boots for months.

The fall guide is how to see the mark: a patch lighter than the bed around it, often in shallow gravel with flow over it. If you see it, walk around it. Fish from a path that does not cross it. Leave a fish that is holding on that patch. A posted closure wins over this page.

8. One line before you rig

Write the temperature, the hour, whether the river is open or shelved with ice, and whether you saw pale gravel. Then one sentence. "41°F at noon, open deep run: a size 20 midge under the indicator, a handful of slow drifts on the soft edge." Or "36°F, shelf ice to the wood: paste the guides, fish that edge from the bank, and quit when the line freezes again."

Winter water, the short afternoon, and the lies trout use when the river is cold get more room in Fly Fishing for Nerds: A Data-Driven Guide to Finding, Hooking, and Landing Trout. Readers can take 25% off ($9.74) with code NERDS25 at Leanpub.

The Riverbank Checklist is the one-page routine for the bank: safety first, then one hypothesis and a short test. Temperature, ice, and whether you saw pale gravel belong in that note.

A reach that was stocked this week is a different first cast than a midge in a spring creek. The stocked-trout guide is the truck, the pool by the stop, and one fly.