Intro:

While many rivers in Washington are closed to fishing until May, there exist fisheries permitting anglers to pursue and keep Mountain Whitefish (Prosopium williamsoni), a salmonid eager to take flies and fight like hell. Do not let the cold or lack of available online content on this species prevent you from some incredible days exploring rivers and discovering this fish.

Over the Christmas holidays, I have spent eight days and over 60 fishing-hours east of the Cascade crest actively pursuing this species for several reasons; chief of which was my desire to improve as an angler. I would like to share my experiences and thoughts on catching these fish in the hopes of providing helpful information on an otherwise minimally discussed species.

I am a relatively new fisherman, knowing only fly-fishing, which I began for the first time mid-June of 2024. Nearly all my fishing experience over this summer was spent targeting small trout (4-8inches) on small streams with a compact 4-weight for a research study, requiring minimal and shallow nymphing with only a dry-dropper setup. My days fly-fishing in the fall were exclusively for salmon, which I found to be much more about lobbing flies as often and randomly as possible in the hopes of annoying a metabolically inactive fish to the point of attack.

Lacking from my time on the water were days spent nymphing at depth and pursuing a steady dead-drift. I knew from my own snorkel surveys in the summer that these fish commonly reside within the bottom 8 inches of the river’s complicated water column, are found in pools, and that they would require well placed flies to attract. Whitefish seemed to be the best off-season practice for summer fishing, and they were.


Additionally, I do not enjoy catch and release fishing for ethical reasons, and Whitefish fisheries allow the keeping of fish. If I cannot keep a sizable and sustainable fish for food, I do not fly-fish. To each their own.

Conditions, Gear and Clothing:

Over my days fishing in December and January, the outside temperature ranged from 4 to 37 degrees Fahrenheit, with the days averaging around 28 (lows commonly at night). The water temperature ranged from 1.8 to 5.6 degrees Celsius in shallow riffles, although I did not take the temperature multiple times a day consistently. I was fishing with 2-3ft of snow on the banks and often while it was snowing. Every day was a varied level of overcast. I used an old, cheap 9ft, 5 weight medium action rod with a 9ft 4x leader and 4x fluorocarbon tippet. I used an orange screw-on foam indicator (it opens in half and screws onto your leader). My net was a small, cheap, trout-sized knotless silicone net with 18x11x7 inch basket dimensions. I wore waders and felt wading boots. I wore wool base layers under Carhartt or military wool pants, and wool flannels under a wool sweater and a down jacket almost every day. I wore a baseball cap and usually a wool hat atop the cap, along with wool fingerless gloves (military surplus). I wore polarized sunglasses.

I found the baseball cap crucial for preventing snow from landing on my sunglasses, which I found to be a necessary piece of gear with the level of snow glare. The wool baselayers I consider to be a safety and comfort necessity when wading in these temperatures. The waders are non-insulated, but worked without issue. The felt-bottom boots are all I have known, and worked well with the slime layer on the rocks.

I would like to experiment with a longer rod and a much longer leader for this style of nymphing. I have only ever known 7.5-9ft rods and I see the application of longer rods after having spent so many hours nymphing on a wider river. There is much about fly-fishing I remain clueless about and if you have insights or thoughts on the matter (or any of what I write), please share them.

The water conditions were consistent, excluding the temperature swings. The water was close to the CFS lows in September. Nearly ⅓ of the river was not fishable due to an ice layer covered with snow, and several kilometers of river consisted of pocket water which I skimmed over quickly.

Habitat:

I found the majority of Whitefish eager to take my fly to reside in the seams in runs beneath riffles, sharing the environment with rainbows, steelhead, cutthroats and the occasional bull trout. In the mornings and on colder days (nights in single digits and water temps around 2 C), Whitefish were found in the softer water closer to the shore, away from the faster-moving main-current. I found them in various depths in these little runs of water, from 18 inches to 4ft, usually within the first 60 meters of the run of water post-riffle. Occasionally I would pull one out from the bottom of the main current in the run, where a good drift is difficult to obtain and short-lived. I am sure many, many fish reside in these main-current areas below riffles, but getting an appropriate drift in front of their face proved hard to achieve.

My father on a good sized Whitefish. Note the shallow riffle leading to a run of water with a main current. The soft-water shoulders were productive.

The holes I fished ranged from 4-12? feet deep, and almost all included extremely difficult and varied current patterns which made obtaining a proper drift very challenging. The deepest whitefish I caught in these holes was likely around 7ft down (I saw the fish take the fly which was around 8ft from the indicator, drifting slowly). I was drawn to these holes due to my snorkeling finding stacked, large Whitefish in holes in the summer, but I found them often too difficult to fish compared to the riffle-areas. However, the three largest whitefish (by far) that I found were in these holes. I fought with three absolute units (I would genuinely guess around 22 inches and 3 pounds), and all three came from deep holes. All three shook out the barbless hooks before I could land them. One of the leading challenges to these often 90 degree river-bend holes was the inability to land a fish in anything but fast, swirling water up to your waist. A more experienced and developed fisherman certainly would have performed better than I, but after almost being swept downstream in my earnest to land a donkey of a fish in front of these holes, I usually only fished them infrequently and briefly. It should be noted that it appeared to me that it was easy to overnymph a hole, relative to a riffle. The fish appeared to become more wary, perhaps due to longer-lived, learned fish or the stagnant current at the bottoms which does not demand a quick strike.

Mountain Whitefish were only found in waters with quite a bit of surface-disturbance, or if not, then in great depth, making spot-fishing them nearly impossible. They were found to be over substrate that was everything from sand to boulders in size. In terms of tolerance of proximity to humans, I found them to be quite willing to take flies 10ft from me, while I was up to my waist in the clear water.

The larger fish, with minimal exception, were found as close to the end-run of the riffle as possible, in the faster water. The smaller fish were nearly always found further downstream of the riffle.

Casts, Rigs:

There was a marked difference in results between a solid and long dead-drift, and a poor drift. These fish preferred a long, natural, total dead-drift. I spent a cumulative two hours or so swinging flies to fish that were previously biting, and caught only one fiercely aggressive rainbow. Switching back to nymphing, instant success. The further cast upstream one can make and maintain through mends, the longer the nymph has to get to its needed depth and be presented to the most fish. The less dramatic your mends, the quicker you and your line can recover from them to be ready to set the hook.

I would advise people to not shy from extremely slow drifts in softer water. These were often very successful, though they required more perception and frequent hook-sets. Hookset on everything.
Do not be afraid to tick bottom frequently. Depth seemed to be one of the most determining factors in catching these fish.

I caught perhaps 5 Whitefish on nymphs that had undergone an extended drift, with me shaking out more slack. At the end of these extended drifts, I would at times slowly recover the fly line back towards me (upriver), and I experienced fish biting or being hooked on these flies that were no longer drifting, but instead stationary or coming up from the depths like emergers. Your mileage may vary.

As mentioned, I used 4x tippet and a 4x leader. I never tried to size down to 5x, but I wish I would have, just to see if this would attract more wary fish.

Half my time nymphing was spent with one moderate to heavily weighted nymph, and the other half was spent with two nymphs. I tied the heavier, larger nymph to the belly of the fly-hook of the smaller nymph for some of these days, and it was not until the end of my time fishing that I learned about applying a nymph to the tag-end of the surgeons loop, and adding a second nymph to the bottom of the added tippet. This was wildly successful, but required very quick and careful removal of the flies from the fish once it was landed. A few death-spirals from the fish and a massive tangle was inevitable.

My indicator was anywhere from 2 to 8 ft away from my flies, and my depth was determined by the current and water depth. On walking-speed water, I found the 1:1.75 depth to leader length ratio to be a good starting point.

Hooking up, Fights, Behavior:

Hook-ups can be as violent as your entire indicator disappearing, leading you to do a bass-master classic panicked hookset and warrior cry, or soft enough to break your heart. I believe that often, they go unnoticed! I found that if I missed one hook-set and let the fly drift further, often another fish would hit it as well, as there are often many close together (or it’s the same fish trying again). I have instinctively lifted my rod very slowly but deliberately for no apparent reason, only to find a good sized fish on the end of my line. These moments are magical. Soft take, soft set.

Mountain Whitefish have the capacity to fight like absolute hell, and in a manner that I found very difficult to manage at times. A consistent theme I found was that the larger fish (16 inches+) would fight less in duration, and with fewer, slower head-shakes. The largest fish I landed and fought all surfaced in their fight, in comparison to the rare surfacing of smaller Whities. Perhaps only two became truly airborne, and none in the classic style of the rainbow (more of a porpoising style).
The smaller individuals are the true devils, often performing the most aggressive, rapid and short head-shakes I have ever had the misfortune of combatting, while maintaining their energy for a surprising amount of time. Consider the whole-body thrashing/shakes of a large cutthroat or bull trout, which can be thought of as the fish harnessing its full body to throw a hook. Now concentrate the motion into just the head of the fish, and multiply the number of shakes/second by 10. These violent, short range of motion, high repetition shakes were very difficult to keep tension against without pulling the hook from or out of the fish’s mouth.

In such head-shakes, I would recommend keeping less tension than you would if you were re-directing a fish or leading him to your net, but not enough to allow belly into your fly-line.
It should be noted that every Whitefish I landed and released appeared to recover faster and more fully than any cutthroat, bull trout and most rainbows that fight for the same amount of time. This appears to me to be an additional, clear reason why this species should be pursued by the catch-and-release angler.

Flies:

Most of the fish were caught on flies I tied. See photos below. I used size 14-20 hooks, mostly 18 and 14. I found zero obvious difference in levels of success with fly size.

I only tried using perhaps 6 different flies. 4 of which caught many fish. More extensive nymph experiments would be needed to come to any sort of conclusion.

I tied two types of flies that worked very well. Both were size 14, barbless, extra heavy nymph hooks. One was with a 3.5mm black nickel tungsten bead head (disproportionally large), with a green/black dubbing, wrapped in a manner resembling larval segmentation. I included a long hackle “mane” around the head of the fly to give it the impression of a metamorphosing bug. This fly often out-competed other flies on my line, and I genuinely believe it is because of the greater density of the fly. The other was a true-to color dull gold/light green caddis larva type fly, with a ring of black dubbing behind a gold 3mm gold or nickel tungsten bead. Some included filamentous, rainbow turkey featherettes (separated from chest feathers) added as a tail to the fly, from a Rio Grande turkey. One day, I was fishing with darker flies (the former fly and a pheasant tail). Zero bites. I switched to this lighter caddis-type fly and it was as if a switch was flipped. Dark day, too.

Dark fly with a huge tungsten head.

The other flies I used which had great success were de-barbed (pinched) size 16 copper john with a dark tungsten head and flashback, and a size 18 prince nymph. The prince nymph was without any tungsten, and very light in weight. I kept it as my tag-end fly above a heavier copper john or one of my homemade flies.

Found in the digestive system of these fish were a variety of size 20 and smaller bugs and sticks and rocks. I am not an entomologist and I will not pretend to recognize most of the half-digested macroinvertebrates. Many living bugs in their intestines looked “grubby”, like tiny inch-worms. Many little caddis flies (size 16-20) in their stick/rock shells were also found.

What Worked:

Soft take, soft set

Set on everything that could be a take. Everything.

Be prepared to catch a fish any second the fly is in the water

Change your depth before changing your fly or location

Let them fight

Land them in deeper water. They freak out more than other trout close to the shallows

First cast can be the most important. Be intentional and ready

Small mends allow for quicker line-tension recovery

Snow acts as extra light. Bright flies reflect even on overcast days

Hook-setting downstream of the fish may be more successful

The Fish:

The Mountain Whitefish I caught (including the ones released) ranged from 20 to 8.5 inches with an average weight of around 16 ounces when gutted. Most 14ish inches. I used a soft tape measure and a kitchen scale good to 0.1 grams, but I did not measure every fish.

Whitefish have a down turned head and neck, with what seems to be a disproportionately small head and mouth. Stretching their mouths (once dead), it appears that a size 4 hook gap is close to the maximum width (shank to point) they may be able to eat. They often can be seen turning sideways in the water to catch their prey. Inspecting their mouths, they have very tough maxillaries, and their upper snouts are also tough. The only soft-part of their mouth appears to be the layer of tissue between their lower jaw and maxillary, which is to each side of them. Due to their sideways eating habits and our tendency to set a hook vertically, it seems plausible to me that they can be more difficult to fight and land without hook-slips because the hook is through such a thin and soft material (he told himself reassuringly).

The fish I caught had gorgeous summer straw/golden brown color that may not appear in the photos well. In the water their fins appear a pale, dark blue. Their bellies were a cream/bone white. The only differentiation I can make between the males and females was the color and protrusion of their vent. Even then I was not consistently able to tell between the two sexes on sight alone. When I felt that a female was more likely to be in my net, I would let it go more often.
I found the deeper and larger fish to have their white bellies speckled with sand grain-sized golden brown colorations.

Conclusion:

These fish are active in cold waters, eager to take flies, and demand attention and respect from fly fishermen. They are beautiful, can fight like demons, taste delicious, and will maintain or improve your nymphing skills in a season where excuses for not going fishing are easy to make. With appropriate clothing and a good attitude, you can achieve incredible days on the water plumbing for these fish on the east side of the Cascade crest, when water levels are extremely wadable and prime for river exploration.