Brachycentrus Occidentalis and Brachycentrus americanus are the two species that comprise the Mother's Day Caddis in the American West that hatch in late April and early May, coinciding with the Mother's Day holiday.
Brachycentrus caddis species are considered to be super hatches only lasting a few days in duration in a single location while progressing rapidly upstream. A hatch that can create blizzards of insects filling the air. There may be no other display of the "safety in numbers" survival strategy in the natural world that can overwhelm and confuse a predator by the sheer volume of insects present than the Mother's Day Caddis.
I have seen the hatches of Brachycentrus occur so dense as to form rafts of adults on the water. On one such occasion, I was fishing a river in eastern Washington state. During the early stage of the hatch, I was able to coax a few fish to the surface with my dry fly imitation. Within a half, an hour, rafts of caddis started to blanket the river's surface. I had found a small pool of surface feeding fish. After 30 minutes of casting to the fish with no takes, I noticed that the fish were not feeding on the surface of the water but feeding just subsurface. I could tell this because I did not see the whites of the mouths but rather only the backs of the fish as they turned downward, stopping their upward momentum just inches below the surface but carrying enough energy to break the surface of the water. A tell-tale indication that fish are feeding just subsurface of the water on emerging pupa.
I switched over to a wire caddis pupa imitation and added some weight to my tippet. -- This was when I was still fishing with affixed weight to my leader, I no longer practice the technique -- I cast up ahead of the pod of fish allowing the fly to sink to a few feet in depth and began lifting my pattern towards the surface. This lifting technique is called a Leisenring Lift, which imitates the upward swimming motion of emerging pupa. I had hit the mark with both the fly pattern and my tactical approach. A half hour of not catching anything in the midst of feeding fish during a caddis blizzard was finally over. I was now catching fish on nearly every single presentation that I had made. After landing 25 fish in the next 45 minutes, the pool was played out.
I returned to my boat and paddled to the nearest take out. At the boat ramp, I had two different guides approach me and ask what it was that I was doing as it seemed that I was the only person on that section of the river catching fish that afternoon. I mentioned to them that in this case where there was an overwhelming number of insects present, the fish shifted their focus away from feeding on the surface to a much more natural and less confusing strategy of feeding on emergers just subsurface. I merely started fishing a subsurface soft hackle pattern. One such “guide” -- the quotations marks around the word guide are a snarky gesture because as he is not a guide, but rather, fancies himself the greatest fly fishier in all the land -- quipped to me that he would “never stoop so low as to fish a fly subsurface.” My only retort was to point out, due to his self-imposed limitations, he will be relegated to sit in his boat and watch me land fish after fish on every subsequent day after that if he kept up that shitty attitude. I have never spoken to him ever again; nobody needs that kind of negativity in the world of fly fishing.
Proven Mother's Day Caddis Patterns.
The species of Mother's Day caddis present two stages that are most vulnerable to predation, the prolonged emergence and the ovipositing diving adults. This flymph works at imitating both. This pattern covers all the small green summer caddis.
I fish this fly with a traditional english wet fly swing at dusk when I need to feel the take.