Big Lost River

GAGE LOCATION

DAY/YEAR
GRAPHS

CURRENT
STAGE/FLOW

WHAT TIME

Big Lost at Chilly

7 30 year

1.15 / 115

1 am

Big Lost at Howell Ranch

7 30 year

2.22 / 284

1 am

BIg Lost near Arco

7 30 year

1.98 /

1 am

CITY

Mackay

NOAA

Accuweather

TWC

Ketchum

NOAA

Accuweather

TWC

HATCH

NYMPH/
LARVA

PUPA/
EMERGER

DUN/
ADULT

EGG-
LAYER

Blue-winged olive

Mahogany dun

Trico

Green caddis

Caddis

Golden stonefly

Salmonfly

Cranefly

Midge

Sculpin

Hopper

Baitfish

Beetle

Ant

If the dam outflow is below 300 cfs, fishing can be decent. If the water is clear you should keep a low profile and use stealth tactics. A 6X or even 7X leader is needed in nearly any condition.

Cranefly action can be sporadic, but you should be prepared for them with adult patterns. Skate your Mackay Special or other imitation across the surface. Size 10-12 patterns work best at this time of year.

Tricos may be active below the dam early in the month, but they'll soon be done; the action starts about 9:30 a.m. It can last until 1:00 p.m. Size 22-24 flies are needed. If you're here in time for the tricos, try a Parachute Trico (like a Parachute Baetis, but black body), Bubble Parachute, or No Hackle for the dun stage. A Polywing Spinner or CDC Biot Spinner can work for the spinner stage. Sunny days will improve the hatch.

Hoppers and hopper/dropper rigs can be productive in early September, but as the nights get cooler you can expect less from the hoppers.

Caddis can make an appearance in the evening.

If trout are not feeding on the surface, your best fly choice will be a nymph, such as a size 16-18 beadhead Prince, Pheasant Tail, Brassie, Copper John, or Hares Ear. If the water is off-color, try a red San Juan Worm.

By the end of the month, expect blue-winged olives to begin their run. Some may be already on the water, but the hatch won't really roll until about the second or third week of September.

Mahogany duns are another mid-September hatch to be prepared for.

Midge activity is sometimes a factor at this time of year, and size 18-20 midge pupa patterns and Griffiths Gnats will work well when trout are sipping the tiny bugs from the surface.

On the upper river (Copper Basin), use hopper and ant patterns, caddis imitations, and size 14-16 attractors such as yellow or red Humpies, Renegades, or Parachute Adams. Big outrageous flies such as a Turcks Tarantula or Parachute Madam X are other options. A Royal Trude or Royal Wulff is always productive up here. You can also entice trout with a standard beadhead nymph, such as a Prince, Pheasant Tail, Copper John, or Brassie. You can team your nymph with another large nymph and dead drift the rig near the bottom, or use it in combination with an attractor dry fly or hopper. The hoppers and ants will depart the scene when the nights get frosty.

See the Rivers in General section for more September fly fishing tips.