Fall Fly Fishing for Trout

Cooler water, shorter days, and the gravel brown trout use to spawn. The lies are the ones you already know how to read.

From the book Fly Fishing for Nerds — $9.74 →

October is a different river than August. The temperature drops, the days shorten, and on a brown trout stream the fish start using shallow gravel. The seams, riffles, and tailouts are still the map. What changes is which of those you can wade.

Use the same loop as the observe page: observe, then hypothesize, then test. The thermometer, the gauge, the light, and one look at the bottom are the observation. One sentence about the lane is the hypothesis. A handful of drifts is the test.

1. What changes in fall

Measure the river before you open the fly box. A hatch chart for “October” is a guess you have not checked.

Water temperature. Nights cool the river before the afternoons do. Idaho Fish and Game calls the lag thermal momentum: the air drops, and the water follows later. When your reading lands in the 50s or the low 60s, you are in the band where trout feed readily. North Carolina State Extension calls 55–65°F the optimum for trout production. Michigan DNR lists a brown trout preference of 50–65°F. That range is warm enough for trout to feed, and below the summer stress band. The water-temperature guide is how to take the reading. Virginia DWR says trout are most comfortable in water that does not exceed 68°F. A warm fall afternoon can still cross that line. If it does, stop.

Lower, clearer water. Idaho Fish and Game notes that many trout streams run low and clear in fall, and that trout in that water are spooky and more often in deeper or better-protected lies. Confirm it on the gauge. The river-flow guide is how to read today’s discharge against that gauge’s own range for the date. A tailwater follows the dam release. A storm can put a freestone back up and back to color the same afternoon. The after-rain guide is that day.

PingWhen (paid, from $9 a month) can email you when a USGS gauge crosses a flow or gage-height level you set.

Shorter days. Idaho Fish and Game ties fall behavior to temperature and daylight together. As the water cools and the days get shorter, trout feed ahead of winter, when food will be scarce. The fishing window shrinks with the light. The evening that ran long in July is over before you have fished two runs. The time-of-day guide is where to put the session once you have the temperature.

Brown trout, before they are on the gravel. Brown trout spawn in the fall. Michigan DNR puts that spawn in tributaries in September and October: the fish move onto shallow gravel, the female digs a redd, and she covers the eggs. Wisconsin DNR’s trout plan has brook trout and brown trout spawning from early October into December, with a peak around mid-November, as water temperature falls and day length shortens. Virginia DWR puts the spawn on its rivers around mid to late November, when the water is in the mid to upper 40s, and describes the weeks from late September into mid-November as the pre-spawn stretch, when male browns are territorial and will chase. Idaho Fish and Game says some of the largest brown trout, brook trout, and lake trout are most aggressive as spawning approaches, and that a streamer can draw the strike. Those calendars disagree because the rivers disagree. The thermometer and the look of the gravel are the check on your water. A streamer along a soft edge is the test for that aggression. Leave a fish that is sitting on a redd.

What is in the drift. Early in the fall, terrestrials are still in the grass. Iowa DNR calls early fall grasshopper time, especially for brown trout, and says an imitation works. If hoppers are in the bank grass, fish the edge they would fall into. If the grass is empty, skip the hopper.

On a gray afternoon, look for blue-winged olives. The North Carolina Wildlife Resources Commission hatch chart lists them from October through December, in the afternoon, in sizes 18–24, and names a blue-winged olive or an Adams. Pennsylvania Fish and Boat Commission’s magazine says these mayflies often appear in cloudy, rainy, and stormy weather, in sizes 16–22, and lists a pheasant-tail nymph, an emerger, and a parachute dry. Catch a bug if you can. The size comes from the insect in your hand.

2. Where to fish

Use the same map as the rest of the year. Name the riffle, the run, and the pool. Fish the soft side of a seam, including the foam line that marks it. On a small stream, the pocket-water checklist still applies: the pillow, the soft edge, one drift. The reading-water guide is the longer version of that walk.

In low, clear water the fish are easier to move off the lie before you cast. Idaho’s note about spooky trout is the reason to wade less, stay off the skyline, and fish upstream of your feet. A tailout is still a feeding lane when insects are coming through it. It is also shallow gravel with flow over it, which is the kind of bottom Michigan DNR describes for a redd. Look at the gravel before you step into the tail. If the patch is paler than the bed around it, walk around it.

If this is a first day on moving water, the first-day guide is the safety and the short plan. Use it on a fall afternoon the same way you would in June.

3. Best time of day in fall

Take the temperature, then use the time-of-day guide. While the water stays in the 50s, morning, midday, and evening can each be a fair session. The day is shorter than it was in summer, so pick one of those windows and fish it.

A gray afternoon is the olive hypothesis. North Carolina times that hatch in the afternoon from October through December. Pennsylvania Fish and Boat ties the insect to cloudy, rainy, and stormy weather. Stand on one lane for two minutes. Olives on the water, or rises to them, and you fish a dry or an emerger. A quiet surface and you stay with a nymph. The dry-fly guide is how to tell a surface meal from a fish that only looked like it rose.

Idaho Fish and Game notes that rainy days can fish well when the water is low and clear, because the fish are less exposed. Rain that stains the river or puts the graph up is a different problem. Read it with the after-rain guide before you wade.

If the water is already in the 40s, you are in the cold band on the time-of-day guide: a shorter session in the warmest part of the day, usually late morning into afternoon. Virginia’s spawn window, the mid to upper 40s, can be that same cold band. Fish the hour. Leave the gravel. When the river spends the day in the 30s and 40s, the winter guide is the next page.

4. A short fly list

Change one thing at a time. The lane and the depth come before the next pattern in the box.

The quiet-surface row is the same opening as the no-hatch guide: one nymph, one depth, one lane. The indicator guide is where the float goes when you cannot see the take. Pennsylvania Fish and Boat lists a pheasant tail among the olive nymphs, which is the nymph already on the gear page.

Virginia DWR’s fall streamer note uses a woolly bugger, in sizes 2 to 6 on larger rivers, and heavier tippet than a dry-fly leader. On a small creek the starter bugger, sizes 8 to 10, is enough for the first test. Fish it where a trout can hold without fighting the main lane: the soft side of a seam, the bank, the wood. Slow the strips when the water is in the 40s. That is the adjustment Virginia’s note makes as the river cools. The retrieve, the leader, and where to throw it are the streamer guide.

An egg pattern imitates eggs that have left the gravel and are drifting. Fish it in a lane downstream of spawning water. Do not cast it at a fish on the redd, and do not wade the gravel to reach the lane.

Tippet follows the fly. Pennsylvania Fish and Boat lists 4X, 5X, and 6X for blue-winged olives. A size 20 dry usually wants 5X or 6X. A woolly bugger in the starter sizes sits on 3X. The tippet guide is what the X number measures. Change the tippet because the fly changed, then repeat the same drift. Two changes in one cast leave you unable to say which one mattered.

5. Leave spawning redds alone

A redd is the nest. Iowa DNR describes active trout redds as areas of cleaned gravel, built by brown trout and brook trout, with eggs that stay in the gravel until late winter or early spring. The instruction is to leave them undisturbed, and to avoid stepping on or near one, in late fall and through the winter.

NOAA Fisheries, in its catch-and-release guidance for inland fish, says to avoid fishing and wading near redds, because stepping on a redd or even near it can kill eggs, and to leave spawning fish alone. NOAA describes a redd as a cleaned patch of lighter, silt-free gravel, generally 3 to 6 square feet, where the female has dug a depression.

On the bank the mark is color. The patch is paler than the bed around it, because the fish have swept the algae and silt off. It often sits in shallow gravel with moving water over it: a tailout, the tail of a riffle, the inside of a gentle bend. That is easy wading, and it is the wrong place to cross. Walk around it. Fish the seam from the bank, or from a path that does not cross the pale gravel.

Leave a fish that is holding on that patch. Pennsylvania Fish and Boat’s classroom note puts brown trout redds from October into November, and says brook and brown trout eggs need water between 35 and 55°F to survive. That range is about the eggs, and it is a reason the gravel stays closed to boots for months after you watched the fish spawn. Wisconsin’s window, early October through December with a mid-November peak, and Virginia’s mid-to-upper-40s spawn, are reasons to look harder in October. They do not mean every gravel bar you see is a nest today. If the patch is paler than the bottom around it, walk around it. A posted closure wins over this page.

Footing still comes first. A low river can hide the next drop-off. Safety and access are the first item on the bank checklist.

6. One line before you rig

Write the temperature, whether the river looks low and clear, the light, and whether you saw pale gravel. Then one sentence. “54°F, overcast, olives in the film: a size 20 dry on the soft side of the seam, a handful of clean drifts.” Or “48°F, no olives, pale gravel in the tailout: streamer the wooded bank, and cross somewhere else.” Run that test. If it is empty, change the lane or the depth.

Fall water, the spawn, and the lies trout use 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, and whether you saw pale gravel, belong in that note.

If the water was stocked this month, start from the truck's list. The stocked-trout guide is that first week: the pool by the stocking point, then one fly.