Riffles are the Life Blood of the River
On almost every river and stream in the Pacific Northwest riffles are the life blood of the river. This is where the bugs live and subsequently become available to trout and migratory steelhead. The riffles are home to stoneflies, caddis and crawler mayflies. Some species of swimmer mayflies also live in the riffles.
Bugs of the Riffles
The following list of bugs are the ones you'll encounter the most when fishing the Lower Yuba River and other tailwaters or freestone streams.
The Blue Wing Olive Mayfllies - BWO's, are of the swimmer group of mayflies. The BWO nymphs live in
sun struck riffles and the runs below the riffles where algal growth is
present. Most BWO nymphs swim to the surface to emerge in the runs below sun
struck riffles, eddy pools and calmer water. Some BWO nymphs crawl to
the edges and emerge at the rivers edges and climb out on sticks and
rocks to make their transition to duns. Heres a link to info on the BWO's http://www.flyfishingtraditions.com/patterns/blue-wing-olive
March Brown Mayflies - The March Brown Mayflies are well adapted to spring creeks and
tailwaters which in some years can provide a welcome dry fly hatch here
on the Lower Yuba River. March Browns thrive in riffles and runs.
They Browse on thin layers of photosynthetic growth that covers bottom
Populations are diminished in tailwater locations after when scouring
occurs which can happen on our Lower Yuba River. Here's a link to info on March Browns
Pale Morning Dun Mayflies - PMDs are well adapted to spring creeks and tailwaters like our Lower Yuba River.
PMDs thrive in riffles and runs.
The nymphs browse on thin layers of photosynthetic growth that covers bottom rocks.
Populations are diminished in tailwater locations after when scouring occurs which is definitely the case on the Lower Yuba. It seems like there are larger populations of PMD's the farther down the river you venture. Here's a link to info on the PMD's
Pale Evening Dun Mayflies - PEDs are adapted to clinging to the substrate of fast water such as riffles, but commonly also inhabit the slow to moderate reaches.
The nymphs are rarely found in the drift until days preceding a hatch.
A few days prior to emergence the nymphs migrate from water with moderate currents to side pools, eddies and shallow runs. Here's a link to PED's
Slate Drake Mayflies - Live in riffles and hey often perch on tangled branches or debris that trail into fast water
They are extremely strong swimmers
They emerge in late afternoons, evenings and just after dark
Look for cast away nymphal casings on the rocks along or just below riffles for indications of hatch. Here's a link to Slate Drakes.
Mother Day Caddis - Brachycentrus - Grannoms - Grannoms build square-shaped cases and live in riffly water or runs with
moderate to fast currents. Here in Northern California the hatch
typically takes place in about April.
They prefer shallower riffles and runs.
The larvae, though cased, often become available to trout due to their
common occurrence in stream drift and an unusual rappelling behavior. Here's a link to Mother's Day Caddis.
Hydropsyche - Are net-spinning caddis don't build a case in which to live.
Instead, they build a rough shelter of gravel and plant debris that they
attach to the sides of rocks.
Hydopsyche prefer moderate- to large-sized streams with warmer
temperatures, somewhat slower currents, and smaller substrate
The larvae of net-spinning caddis periodically crawl out of their
shelters, let go, and drift downstream 40, 50, or even 100 feet. This
activity occurs on a daily cycle, and peaks near sunrise and sunset. Here's a link to Hydropsyche Caddis
Skawala Stoneflies - The Skwala stonefly nymphs habitat is quick choppy riffles with a substrate of large gravel and cobble. Prior to adult emergence the nymphs migrate to the banks where they crawl out of the water when ready to become adults. Usually they crawl out on the banks, large rocks or even a limb or log. Trout tend to feed on them along the banks when the hatch starts. Here's a link to Skwala Stoneflies.
Yellow Sally and Golden Stone Stoneflies.
Like the other stoneflies, nymphs their preferred habitat is quick choppy riffles with a substrate of large gravel and cobble. Prior to adult emergence the nymphs migrate to the banks where they crawl out of the water when ready to become adults.
Here's a link to Yellow Sally's
Here's a link to Golden Stones
You can go to the Fly Fishing Traditions Lower Yuba River Hatch Chart to get recommended patterns to match them. Here's the link to the Lower Yuba Hatch Chart
The link is also at the top Navigation Bar at the Top of the Blog.
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