Fishing the South Fork of the Boise at 300 CFS

We're getting into 'that' time of year on the South Fork of the Boise. Flows are down to 300 CFS and the river's about a quarter of it's 'summer size'. Fishing can be fantastic through late summer/early fall, but you'll have to change your approach.

The weather's changing, hatch cycles are overlapping, flows are down, water's as clear as it will be all year, and fish are condensed. There are a lot of positives in that list, but changing up tactics is an ABSOLUTE if you're looking to stick fish. Let's look at each of these individually and break down the good and bad.

The Weather's Changing

Two things regulate hatch activity -- temperature and flow. As these change, hatches fluctuate (activate and shut off). Late summer and fall is a very comfortable time of year for river dwellers -- fish, bugs, eyeball pecking birds, beavers, and otters.

The good? The season transition gets things stirring. Bugs pop through a majority of the day so fish can feed actively on the surface from sun up to sun down. You won't have to spend much time waiting around for 'things to happen'.

The bad? Rapid and sporadic weather shifts (rain, wind, lightning) and shorter days. You're going to spend less time on the water in fall but if you do things right, it should be far more productive.

Hatch Cycles Are Overlapping

Late Summer/Early Fall on the South Fork is an aquatic entomological freak show.  The summer to fall transition is about variety and numbers for many stream bottom dwelling critters.

The good? Well, through mid November you're going to see a good number of the following bugs overlapping and hatching throughout the entire day:

• Caddis
• Pink Cahills
• Flavs
• PMDs
• Midges
• Craneflies
  
• Hoppers
• BWOs
  
• October Caddis

The bad? That laundry list of bugs gives fish more choice than what most anglers have stocked in their boxes. Aside from terrestrials (Hoppers, Ants & Beetles), you're looking at various stages of emergence within each.

Needless to say, fish aren't short on menu items. Your job is to do your best to manage the range of stages and pay attention to what they're eating. This can be overwhelming, but conscious observation and patience will make all the difference.

Flows Are Down

We're at 'wading' flows on the South Fork (300 CFS). That said, you need to be IN the water…not ON it. There's only one reason to be in a boat this time of year -- you're disabled. You need to work banks on foot. Boats are great for the 'high water' season (late May through late August), but at this stage of the game you're looking at diminishing returns...and you're boogering water for others.

The good thing about low water? It's easy to get around the river and fish are concentrated. Holding lies are abundant and much more obvious (rock gardens, current seams, foam lines, flats, and transitions from fast to slow and shallow to deep).

The bad? You guessed it. It's easy to get around and fish are concentrated. In a good number of instances, if you bust (or catch) one, you bust the rest. Moving around becomes a bit more tricky. Patience, observation and methodical movements are a must.

Water Clarity

The South Fork of the Boise is a dam fed, tailwater river. The storage in the reservoir has been warmed and insulated by the summer heat for the better part of four months. With minimal water movement, direct sun, and day time temps between 75 - 85 degrees viscosity is at it's lowest point -- that's why the river appears to be so clear this time of year.

The good? Fish spotting becomes a little easier this time of year. The bad? Human spotting (from a fish perspective) becomes a little easier this time of year.

Fish Are More Condensed

With 60 to 70% less water in the riverbed, the fish have to go somewhere. That said, reading structure becomes a little more obvious this time of year. It's not necessarily a 'find one, you find them all' type of scenario, but if you find a productive piece of water (adequate depth, comfortable speed, food and cover), you can just about bet you'll find better numbers of fish taking advantage.

The good? It's possible to get into a lot of fish in a small amount of space. I've been on the river on certain days in late summer/early fall and have not moved more than 100 feet all day.

The bad? Three words: Whack-A-Mole. With varied and prolific hatches, and so many fish in small, prime feeding areas, things can get tough really quickly. This time of year it's essential to focus on a single fish and stick with him.

Playing 'the game' will only get you to the point of pulling your hair out. Watch individual heads and do your best to identify two things -- the type of insect he's keyed in on and the stage targeted. Some fish will take various emergers and cripples, some will be focused on adults, and some may be taking anything within the feeding lane.

All that said, focus on stealth, observation, patience, casting economy, timing, and structure. Fall fishing success is a matter of dialing in on all of these variables.

One last tip…lengthen your leader. 10' to 14' 5X is the standard in lower water. There are a lot of funky micro currents that cause pulling and dragging this time of year. You'll do much better if you've got a little slack in your line to absorb some of that.

We're getting into the best fishing of the year! Slow it down a bit and work the water the way it was meant to be worked -- on foot! It will make all the difference.