Scientific Name: Brachycentrus occidentalis
Common Name: Mothersday Caddis, Grannom, Apple Caddis
Hatch Status: super hatch, can cause caddis blizzards
Color: Pupa apple green, adults black
Location: Western United States, mostly west of the continental divide
Season: Late April early May
The Mother's Day caddis can be an amazing sight to behold. Clouds of millions of caddis can create what appears to be a biblical plague about to descend upon the river. I have seen mats of caddis clumped together forming rafts of mating caddis. The survival strategy for this species is to overwhelm predators with sheer numbers so even gluttonous predation cannot have an impact on population.
Emergence can be the most important stage to fish this hatch. While many anglers are more than eager to begin the fishing season with some dry fly action, and having clouds of adult caddis in the air is enough to make any dry fly aficionado salivate, dry fly fishing is NOT the best method. The reason is that emerging pupa can take time to reach the surface and are easily targeted by fish. However, although the surface of the water may seem to be teeming with caddis, fish cannot target them as effectively in such large numbers. Fish would rather not move too far from a comfortable feeding lane in order to feed and especially if food is readily available right in front of their nose.
Pupa can get stuck in the surface film for a considerable period of time, documented up to 30 minutes. If you do see what appears to be surface feeding activity, chances are high that the fish are feeding on pupa rather than adults.
A few years ago I was fishing the Mother's Day caddis hatch on the Yakima River out of Ellensburg, Washington. Around 4:00 in the afternoon the hatch commenced. It wasn't really a hatch, but rather, rafts of caddis that would eventually blanket the pools and back eddies with adults.
I floated downstream to a pod of fish I found actively feeding. I pulled my boat over and waded into a position, so that I could get a good drift. I cast a dry fly a few times with no interest when I started observing the fish behavior right in front of me. The fish were actually feeding subsurface even though they broke the surface of the water. I did not see mouths open, but instead, porpoising fish were chasing emergers upwards in the water column with so much momentum, they broke through the surface and turned downward. Less experienced anglers would have continued casting a dry fly at these fish. In fact, that's what I observed every boat that floated past me doing, casting dry flys in the midst of a biblical plague of caddis.
I clipped off the dry fly I was using and rifled through my fly box for something that I thought I could use to mimic the pupa emerging. I had a few Kauffman's Hot Wired Caddis, a relic of the 1990's in my box; although some hooks were too rusty I found a couple flys that would still work: metallic green wire with a dark dun CDC collar.
As soon as my fly was submerged to about a foot in depth, I felt the line tighten up on a fish. I fought the feisty little native redband trout for a minute and released it. At this point, a guide boat pulled into a transition zone across the river from me and anchored up and allowed his clients to cast dry flys at some feeding fish. I landed another eleven fish when they pulled anchor and rowed on. I recall being into a fish on almost every single presentation for an hour, and I was into a fish whenever a guide boat drifted by.
It was getting dark, the hatch was slowing down, and I had finally put the pool down after 24 fish. I waded back to my boat and rowed to the take out boat ramp. As I was gathering my stuff and waiting for my shuttle to arrive, I was interrogated by one of the regional guides about what I was doing. Apparently, I was the only person actually catching fish that day. I asked him what he was using and he replied that they had been casting dry's. I explained to him the issue, that the fish weren't feeding up top. He adamantly refused to fish with any other technique than a dry fly. I exclaimed he would thus be relegated to watching guys like me catch fish while he flogged the water.
To this day, I still take guests out to fish this hatch, and every single one of them gets excited at the first opportunity of the season to fish a dry fly. Sure, you may catch trout on the surface when this hatch is sparse, but if there are millions of insects in the air and on the surface, the fish will get turned off the adults and focus on the easier pupa instead.
I do not offer dry fly patterns for this hatch as they simply are not needed. I do sell a couple of really effective caddis pupa for this hatch.
The little caddis pupa is hard to tie but oh so worth it! Tied with a black nickle brass bead so it is not too heavy or too bright so that you can swim it through a favorite trout pool during the evening caddis hatch.