A brown trout over twenty inches has stopped living on mayflies. Somewhere in its second or third year it started eating sculpins, crayfish and smaller trout, and from that point it feeds less often, in bigger meals, mostly in the dark, and from the deepest cover the river offers. Catching one on purpose is a different activity from trout fishing, with different hours, different gear and a different definition of a good day. This page is about that activity only. Brown trout biology and general holding water are covered on the brown trout guide.
The fall pre-spawn window
The most reliable time to find a big brown in reach is the month before it spawns. Browns spawn in fall, and in the weeks before they move upstream, stage below riffles and pool tails, and become aggressive toward anything that comes near them. The river pages on this site say it consistently. The Yellowstone through Paradise Valley reports pre-spawn browns of twenty to twenty-six inches encountered regularly in fall. The Madison calls its September and October pre-spawn browns among the most aggressive fish in Montana. The Gunnison Black Canyon, Frying Pan, Big Hole and New Fork pages all name fall pre-spawn as the big-fish season. On the Green River, the C section through Browns Park is where the river's reputation for big browns comes from, and fall is when they show up after the rainbows have gone quiet.
The ethics are simple. Fish the staging fish in the pools and runs below the spawning gravel. Do not fish redds, do not wade through clean gravel in tail-outs from October on, and leave paired fish alone. Some states close specific reaches or set gear rules during the spawn; check the agency for the river before you plan a fall trip, because those rules change.
Low light is not optional
Big browns feed in the dark and in the transitions on either side of it. On a bright day in clear water, the fish you want is under a cutbank or a logjam and will not move for a fly. The North Platte page describes the Miracle Mile browns as strong nocturnal feeders and says evening and night fishing there is productive; the same is true of every river on this list. Plan around it: on the water before first light, off it by mid-morning, back an hour before sunset, and stay until you cannot see the bank. Overcast, rain and off-color water are the exceptions that make midday worth fishing, because they take the sun off the fish. A rising river after a storm, clearing from brown to green, is the single best daytime condition for big streamers.
Big streamers, and how to fish them
The fly for a big brown is a big fly. Articulated streamers in the four-to-six-inch range, sculpin patterns with heavy heads, and double-hook rabbit-strip flies in sizes 2 through 2/0 are the tools. Olive, black, white and yellow cover most conditions; darker in low light and dirty water, brighter in clear. They need a 7- or 8-weight rod to cast all day, a sink-tip or full sinking line to get down along the banks and canyon walls, and a short, stout leader of 0x to 2x. Fluorocarbon matters less than getting the fly deep and moving.
Retrieve matters more than pattern. A big brown usually eats a streamer that is fleeing or wounded, not one that is swimming steadily. Strip hard and irregularly, pause, let it drop, strip again. Fish the fly down and across the deep edges and the seams along undercuts, and swing it through the tail of every pool. From a boat, pound the bank: cast tight to cover, three or four strips, pick up and cast again. The Green page describes exactly this in the B section, where browns are worked along the canyon walls and through the deeper bends of Browns Park.
Mouse patterns after dark
Night fishing with a mouse is the one technique that regularly moves the largest brown in a river, and on the right rivers it is the only technique that does. A deer-hair or foam mouse in size 2 to 6 is fished on a floating line and a short, heavy leader, cast across and slightly downstream, and swung or slowly stripped so it leaves a wake across a slow pool or along a bank. The take is usually a heavy boil, not a splash. Wait until you feel the weight before setting. It is slow, and it requires knowing the water in daylight first, since you will be wading and casting by feel. Night fishing is not legal on every river; some states and some park waters restrict hours. Check the agency for the water before you go.
Big water grows big browns
A trophy brown needs room and food, which means the rivers on this site that produce them are the big ones and the rich tailwaters, not the small freestones. The candidates here:
- Bighorn River, Montana: browns over twenty-four inches are encountered on most full-day floats, most active during fall streamer fishing.
- Taylor River, Colorado: wild browns averaging sixteen to twenty-two inches in a Gold Medal tailwater.
- Provo River, Middle section, Utah and the Weber: Utah's largest accessible browns, holding under sod banks.
- Gunnison River, Colorado: Black Canyon browns that may average eighteen to twenty-four inches because almost nobody fishes them; the descent and climb out are serious.
- East Walker River, Nevada: desert tailwater browns, with fish over twenty-four inches noted.
- North Platte, Miracle Mile, Wyoming: browns averaging sixteen to twenty-two inches and feeding at night.
- Yellowstone River, Montana: the biggest freestone on this site, with fall pre-spawn browns below Livingston.
Gear and a realistic day
An 8-weight with a 250- to 300-grain sink-tip, a spare spool with a floating line for mice, a dozen big streamers in three colors, a mouse or two, and 0x to 2x leader material. A net big enough to hold the fish you are after, and a plan to keep it in the water for the photograph. Then a realistic expectation: a trophy brown day is often one eat, and many are none. Fish from dark to mid-morning, rest, fish from evening into the night, and count the follows and boils as the day's score. The fish that turns on a streamer and does not eat it is still the fish you came for, and it told you where it lives.