Bugs – The Yuba Skwala Stone

It’s late January and the word on the streets is that the Skwalas are out. It’s time to tie up some big bugs and get ready. The last time I fished the Yuba I picked up a couple of nice fish with a Mercer’s Skwala Nymph. It’s a good one.

The Skwala activity on the Lower Yuba River can start as early as late December and then transitions to “strong” activity beginning mid February and generally lasting until mid April. The Skwala is a very important hatch in that it is the first big meal of the season. Regardless of how many adults there are, the fish know they are there. Fish make their living on eating the predominant insects and food sources of the season.

If you’re fishing on the Lower Yuba River and someone asks you what pattern to use for the Skwalas, tell him without breaking into a grin, “Try a Skwala Emerger”. Like all stoneflies, Skwala’s crawl from the river and actually hatch on riverside rocks or vegetation, so there is no emerging period when they are available to trout, just the nymphs and adults. Hence, no emerger patterns for Skwalas.

Skwala nymphs are predatory and feed on other aquatic insects during their one year spent maturing in the river. I heard from Frank Rinella that Ralph Cutter has a theory that the Skwalas are munching on the caddis and that’s why we haven’t seen as many of them on the river. Who knows? If that’s even remotely true, there must be a lot of Skwalas!

Once spring starts knocking on the door they crawl from the water, hatch as adults, and go about the business of finding a mate, an interesting process for stoneflies. They will locate mates by “drumming” their abdomens on the branches of bankside willows, a potential mate will “drum” back, and this heated “Mating Game” will continue until a match is made or they give up and try to find another mate. Another interesting aspect of skwala stoneflies is that only the females have wings, and is one of the reasons that skwala dry fly patterns will often incorporate a black egg sack. The females are the ones most often available to the trout while the males are busy crawling around on dry land, drumming up lost love.

In Mid-February (on the average every year) the water temps start to increase a bit. Water temps are always the impetus for insect emergence. The Skwala nymph starts getting active around 39-40 degrees. Just think about it. It has been a while since the trout were gobbling up eggs and they have been eating small mayflies for awhile. The rainbow trout and steelhead are getting into their pre-spawn mode and the larger trout are thinking about perpetuating the species. Their metabolism is starting to pick up a bit from the previous two months of colder water temps and they will most certainly chow down on larger types of food sources and also to prepare for the spawn. Once the water temps start coming to about 45 degrees the bug of choice is the Adult Skwala. Time to tie, buy, beg or steal Skwala Dry patterns.

The Skwala nymphs prefers fast moving, well aerated, cold, clear water with a rock and cobble bottom. This is probably why the Skwalas are present on the lower Yuba River. The nymph generally emerges in the late afternoon and into the evening. Stonefly nymphs are generally pretty poor swimmers and Skwala’s are no exception. They swim, or at least attempt to, in a side-to-side type motion with most of the movement taking place on the upper body and the tail kind of dragging along.

They are still prone to getting caught up in the drift once they become very active and start heading for the banks. Fish will stage in the shallow riffle areas and will actively search for the adults drifting along the banks and under the willows. Be careful not to step and wade into areas that could be holding opportunistic fish looking for a big meal.

The Skwala hatch on the Lower Yuba River is the real deal! It is not a prolific hatch, yet it is an important food source that helps kick off every new season. Get ready! They’re coming!

Entomology of the Yuba Skwala Stone

SKWALA STONES

Entomology: – Skwala Stonefly – Perlodidae

Order: – Plecoptera (Stonefly)

Family: – Perlodidae

Sub family: Perlodinae

Genus: Skwala

Species:Americana (American Springfly)

Skwala Nymph Characteristics

Yuba Skwala Nymph

Color – Dirty Olive with a slight olive tinge, lighter on bottom sometimes yellowish

Size – 17-21mm

Defining Physical Characteristics – Two long antennae, two tails, 2 separate pair of wing pads, 3 sets of legs, external hair-like gills between legs, t-shaped claws at end of each leg.

Skwala Adult Characteristics

Yuba Skwala Adult

Adults Color – Olive to dark brown with mottled orange around the legs

Size – 17-21mm

Defining Physical Characteristics – Adult female Skwala’s will have a pronounced egg sack dark purple to black in color and about 2-3mm in diameter under their abdomens. The female Skwala sits low in the surface film while she is depositing her eggs and will be readily available to trout.

Techniques for the Yuba Skwala Stone

When are the times to imitate Skwalas to be successful

  • As active nymphs they are often found in the water/food column for the trout, being knocked loose and free drifting. This is especially true during pre-hatch periods when their movement activity increases dramatically.
  • They are also available to the trout as the female adult returns to the water to lay eggs.
  • On a windy day as the adult is blown on to the water.
  • As a spent adult that falls on the water to die.

How to Present Imitations

  • Use as either an impressionistic searching fly or as a realistic imitation when matching the hatch
  • Drift the fly through different water types; faster riffles and shallower water near the banks of a river with moderate to slow currents are the most productive water types for this fly
  • Skwala stoneflies are available to trout during the early season (January – April) on the Lower Yuba River
  • Hatches occur consistently and with long duration throughout the daylight hours
  • Strikes on skwala stoneflies are often far from subtle because trout must often be prepared to rip these strong clingers from their rocky homes
  • When approaching a shallow water environment with a stonefly imitation, be extremely careful not to spook happily feeding trout

How to Rigg for Nymphing

  • Set up for nymph fishing with a two or three rigg under indicator.
  • Rigg with a tapered 9 ft 2x or 3x leader to a tippet knot.
  • Add 12 “ of 3x fluorocarbon to your favorite Skwala stone nymph imitation (Mercers Skwal Stone, hint)
  • Put split shot at the tippet knot above the stonefly nymph. The knot will stop the split shot from sliding down to the fly.
  • Tie 4x Flurocarbon tippet to the hook bend of the Stonefly nymph and extend 12” to 16” to a caddis pupa dropper.
  • Tie 5x Flurocarbon tippet to the hook bend of the caddis pupa nymph and extend 12” to 16” to a mayfly BWO or PMD nymph.

How to Rigg For Dries

  • Rigg for a standard dry fly presentation
  • Use a tapered 10 ft. 4x tapered leader
  • Extend tippet using 4x flurocarbon 24"(+/-)
  • Attach your favorite Skwala Dry pattern

Clay’s Fly Box


I always look forward to the Skwala hatch, it’s probably because it’s the first sign that the bugs have survived the winter flows, and is really the first viable hatch of the year. This year I’ve really worked on refining nymph and dry patterns to match the Skwala Hatch. The thing is that there isn’t a Skwala pattern on the market that really matches the size and coloration of the Skwalas hear on the Lower Yuba. The Yuba Skwalas are more yellow with a hint of olive, and I’m talking a hint. That’s the key.



Here’s a list of patterns the I carry including the new Skwala prototypes, “The Skwalanator” and the “Knothead”

Patterns for the Yuba Skwala Stone

Pattern Overview

Most Dry Skwala patterns are imitated by a Stimulator type pattern. They are tied in a size #10, with a 3x long hook. It is important that your pattern sits low in the surface film. If you watch the female adult on the water, you will see that it looks like a stick with moving legs. The low riding Skwala Dries should have the female’s prominent black egg sack. Trim the hackle on the bottom of the fly so it will to settle into the surface film.

Nymph Patterns

Clay’s FFT “Yuba Skwala Nymph”

This is my variation of Mercers’s Skwala Nymph. I’ve used rubber legs for the tail and the body is dubbed with a yellow dubbing with olive thread. The key is to dubb this sparsely on the thread so the olive color shows through the yellow dubbing and give the body a yellow-olive cast.

Hook: TFS 2302, sizes 10-12

Thread: 8/0 Uni Thread, olive

Antenna: Ringneck Pheasant Tail Note: You put the tungsten bead on before you put the hook in the vise and let it dangle by the hook bend while you tie in the antenna. You then tie the two pheasant tail fibers on facing forward over the eye of the hook. Whip finish the thread. Cut. Move the bead up into position at the eye of the hook and then re-tie on the thread, and away you go.

Bead: Tungsten Bead, black – match to size

Tail: Turkey Biot Quills, Yellow

Rib: Black Wire, match to size

Carapace: Thin Skin, Black

Abdomen: Yellow J. Fair Dubbing

Thorax: Yellow J.Fair Dubbing

Wingcase: Thin Skin, mottled Black

Legs: Tarantula Legs, Mottled Brown

Anderson’s Rubberleg Stone

This pattern was developed by George Anderson of Yellowstone Anglers. Tie it in colors to match the Skwalas in your area.

Pop-Up-Box Anderson’s Rubber Leg Stone

Anderson’s Rubberleg Recipe:

Hook- TMC5263 with weight added

Thread- Dark Brown 3/0

Tail- White round rubber leg sections

Abdomen- Cream on bottom to match hares ear thorax and medium brown woven synthetic fuzzy yarn on top

Legs- White round rubber leg material

Thorax- Medium brown hares ear and muskrat dubbing left shaggy.

Hogan’s Rubber Leg Stone

Hogan created the Yuba Rubber Leg Stone to more accurately match the shape of true stonefly nymphs. He incorporated some of the best elements of a standard rubber leg nymph but incorporated a few elements to give the pattern a more realistic profile. It is named after the Yuba River so for these that are fishing it I’d recommend trying it.

Pop-Up-Box Hogan’s Rubber Leg Stone!

This is Hogan Brown’s stone fly pattern. Like many of his patterns it’s a keeper!

Jimmy Legs or Superfloss Rubberlegs

The Jimmy legs is a new pattern that is basically a standard rubber legs with knots in the rubber legs. Does this make it better. Who knows you try it and let me know.

Pop-Up-Box Jimmy Legs or Superfloss Rubberlegs

Superfloss Rubberlegs

Hook: TFS 5263, sizes 4-8
Thread: 8/0 Tying Thread, camel
Body Weight: Lead-Free Wire, 12-20 wraps of .025
Tail: Super Floss Stretch Body Material, color to match
Legs: Super Floss Stretch Body Material, color to match
Antennae: Super Floss Stretch Body Material, color to match
Body: Chenille, brown

Pattern from www.theflyshop.com
You can get the tying materials from there too!

Mercer’s Tungston Skwala Nymph

Pop-Up-Box Mercer’s Tungston Skwala Stone

This fly has been a producer for me wading and fishing the dropoffs below riffles in February through March. I either use indicator methods or tight line nymphing methods and work the drop offs heavily.

Mike Mercer’s Tungsten Skwala Nymph Recipe

Hook: TFS 2302, sizes 10-12
Thread: 8/0 Uni Thread, olive
Bead: Tungsten Bead, black – match to size
Tail: Turkey Biot Quills, olive
Rib: Gold Wire, match to size
Carapace: Thin Skin, mottled olive
Abdomen: Mercer’s Buggy Nymph Dubbing, z-wing caddis
Thorax: Mercer’s Buggy Nymph Dubbing, z-wing caddis
Wingcase: Thin Skin, mottled olive
Legs: Sili Legs, olive/black flake
Antenna: Ringneck Pheasant Tail

Pattern from www.the fly shop.com
You can get the tying materials there too!
Hogan’s Bottoms Roller is another good looking stone fly nymph.

Willie’s Yuba Skwala Nymph

Willie’s Yuba Skwala Nymph Recipe

Hook: TMC or Targus 200R #4-14
Thread: Black
Abdomen: Copper Flashabou or Braid
Collar: Peacock Herl
Underwing: 4 Peacock Herl Tips
Overwing: Copper Flashabou
Hackle: Guinea
Optional: Copper bead

The People’s Stonefly

Pop-Up-Box The People’s Stonefly

HOOK: Dai Riki 700BB, sizes 6-10
THREAD: To match body color
UNDERBODY: Lead wire or tape, flattened and cut to shape
TAIL: Golden-brown goose biots, tied in a “V”
BODY: Tan Kaufmann’s blend
BACK: Brown Body Stretch
RIB: Fine brass or copper wire
THORAX: To match body
LEGS: Two pairs of black rubber legs
WINGCASES: Three sections of brown body stretch, cut into “Vs”
ANTENNAE: Golden-brown good biots, tied in a “V”
HEAD: Brass bead

Skwala Dries

The Skwalanator

Pop-Up-Box The Skwalanator

I’ve been on a quest since last winter after being humiliated by refusal after refusal of every Skawala dry fly I had in my box, to come up with a better pattern to match the Skwalas on our local Lower Yuba River. I had decent luck last February and March with the standard patterns I carry when fishing the nervous types of water, but when the fish would move down into eddy type water or the flats below riffles where they could really take a good look at the flies, no takers. They turned up their noses and said “Fakers go home!” They would take live Skwalas inches from my dry fly put no dice.

I came up with this pattern after purchasing just about every pattern available, I think I collected about 16 patterns. From these patterns I took what I beleive was the best attributes and came up with the “Skwalanator”. It’s a prototype fly and I’m not going to crow much about it until I can put it to test this spring.

Recipe for the “Yuba Skwalanator” (Arnold is still Governor by the way).

Hook: Tiemco 2312, Size 12 (This is the first major change. The Lower Yuba Skwalas are smaller than most patterns in the market)

Thread: 6/0 or 8/0 Black ( I like to use the 8/0 because of the many materials used in this pattern.

Egg Sack: 1/8" black foam cut to 3/32" wide. (Double over and tie about 1/8" past the hook bend.

Palmered Hackle: Black Dry Fly hackle size 14

Body: Antron dubbing Yellow, dubbed onto olive thread. ( This is the second major change from all the patterns on the market. The Skwala on the Yuba river are more Yellow Olive (with emphasis on the yellow)

Under wing: Hareline No-Fray Wing Material Black (Fine mesh wing material like micro window screen)

Over wing Flash: 5 to six strands of Krystal Flash

Wing: Dark Brown Deer Hair – (Sparse Wing)

Dubbing at Thorax: Antron dubbing Yellow,

Rubber Legs: 2 pairs of Tarantula Fine Round Rubber Legs, Brown

Hackle: Black Dry Fly Hackle size 14

That’s a lot of materials to fit on that size 12 hook. Minimize your wraps and dubb with very small amounts of dubbing. Sparse!

The Knothead

Pop-Up-Box The Knothead

I’m trying to refine two types of Skwala dries, one for the bouncier, nervous water, which so far is the prototype “Skwalanator” and now I’ve come up with a slow, eddy water prototype pattern I’m calling the “Knothead”.

The resident rainbows will take a Skwala Dry with reckless abandon sometimes in the nervous moving water when the Skwalas are in the drift, many patterns work, some better than other. When the fish are staged in slack or eddie water feeding on the helpless Skwalas it’s a different story, a much more imitative pattern is required. Twitching the fly can help but I’m convinced that you need to get (1) the profile correct (2) the size correct and (3) the color much closer to the natural. Thus the need for two separate patterns.

This is all conjecture and experimentation and will hopefully be put to test in January.

Hook: Tiemco 2312, Size 12

Thread: 6/0 Olive (I like to use the 6/0 for the deer hair bullethead)

Egg Sack: 1/8" black foam cut to 3/32" wide. (Double over and tie about 1/8" past the hook bend).

Rib: Black wire

Body: Yellow antron dubbing wrapped with the Olive thread (When the yellow dubbing is wrapped with the olive thread the olive color blends with the yellow dubbing to give it the yellow/olive cast that you need to match the Yuba River Skwalas.
This is the second major change from all the patterns on the market.

Under wing: Hareline No-Fray Wing Material Black (Fine mesh wing material like micro window screen)

Over wing Flash: 5 to six strands of Krystal Flash

Bullethead/Overwing: Dark Brown Deer Hair – (Sparse Wing)

Rubber Legs: 2 pairs of Hareline Fine Round Rubber Legs Black or Tarantula legs Fine, Mottled Brown

Visible Over Wing: Small bunch of orange dyed Deer Hair

Once the fly is completed, carefully trim the deer hair overwing and remove all the deerhair at the bottom and on the two sides until you get the desired profile of a sparse overwing. I’ve left some on the sides as I just think it makes the fly look buggier. If the trout don’t like it I’ll just trim more off the sides.

Stimulator, Olive

Pop-Up-Box Stimulator – Olive

Stimulator, Kaufmann’s (Olive Color Scheme)

Pattern Recipe: Hook- TMC200RBL sizes 8-18

Thread- Fluorescent Fire Orange 6/0, Tail

Light gray elk hair, Rib- Fine gold wire

Ribbing Hackle- Grizzle hackle undersized and palmered over body

Abdomen- Olive fur or Antron dubbing

Wing- Light gray natural elk hair

Hackle- Grizzly palmered over thorax

Thorax- Amber Angora goat dubbing.

Video of the Yuba Skwala Stone

The Stonefly