Mercer’s Missing Link

I t may seem strange that caddis run second fiddle to mayflies as our preferred fishing option. On paper, caddis are clear winners — nearly 500 species to mayflies’ 100, abundant in all environments, and they hatch over more of the fishing season. Their downfall is the fickle nature of the trout targeting them.

Most of the time, mayfly feeders are reasonably predictable. Perhaps a nymph early in the hatch for fish targeting the naturals as they rise from the stream or lake bed, then onto an emerger once the fish start rising. Even fish taking fully emerged duns will usually still take the emerger — just match the size of your fly to the size of the naturals. Mayfly spinner feeders can be a little more difficult, particularly in lakes, but that seems to be accepted. Perhaps a payoff for the easier dun feeders.

Caddis feeders on the other hand can be more arbitrary. When taking pupae they need the fly rising right in front of them at just the right moment, while those fish actively rising key in on either the emergers or the adults, totally ignoring one or the other.

On the central Victorian lakes the fish have an annoying habit of quietly picking off caddis emergers in the calm flat water, while slashing wildly at fluttering adults in the breeze-ruffled zones. A fickle breeze can see you changing flies more often than casting. Most frustratingly, what works one day will be completely ignored the next, despite similar conditions.

Fly pattern can make a difference with these fussy caddis feeders, and one that has stood the test of time is Mercer’s Missing Link. Mike Mercer developed this fly while chasing caddis-feeding rainbows in the Lower Sacramento River in California. His thought was to imitate the spent adults, something not covered by the usual patterns, and it was designed to highlight the sunken body and swept back wing of the natural spent caddis.

The Missing Link found immediate success, not only as a spent pattern but in all stages of the hatch. It can be dead-drifted as an emerger or spent adult, or drawn across the surface for fish chasing fluttering adults. For pupa feeders, hang a pupa pattern 40 cm below, then draw your flies with a steady pull as the fish comes close. They often move to investigate the skating dry, then take the pupa as it rises in front of them.

When tying a Missing Link, start your thread behind the hook eye and begin to lay an even base down the shank. At about the halfway point tie in a single strand of UV Krystal Flash for the rib (later). Tie down the Krystal Flash as you continue the thread base down the shank and slightly around the bend. Then form a thin slightly tapered abdomen as you wind back to the midpoint on the shank.

Wrap the Krystal Flash forward with 5 or 6 turns and tie off, then add a thin coat of head cement or your preferred epoxy. This is to protect the fragile rib rather than build up any bulk. Finish the body by twisting a small amount of dubbing onto your thread and building up a small thorax just in front of your tapered abdomen.

For the down-wings select a small amount of synthetic fibre — here I have used Enrico Puglisi (EP) Trigger Point Fibers but there are many similar types. Trim a length about 2 inches long and attach it in at its midpoint on the far side of the shank just in front of the thorax. Secure with three or four tight wraps of thread. The rear half forms the backwards sloping wing on the far side. Bring the other half over the top of the hook shank and back along the near side of the shank, securing with 3 or 4 tight turns of thread. You should end up with a wing facing back on either side, roughly parallel to the hook shank.

Select a hackle and strip some barbs from the bottom of the shaft, or rachis, then attach in front of the wings for wrapping later. Finish with your thread at the halfway point between the wings and hook eye.

Next, clean out the under fur and stack a small pinch of elk or deer hair. Measure the hair against the hook and tie it in forming a wing, a shank length long, much like your standard Elk Hair Caddis wing, but do not trim the butts yet.

To make a post of sorts to form the parachute hackle around, lift the tips and butts of the hair up and make a firm wrap or two around the base, finishing with the thread in front of the hair. While still holding the hair up, wrap the hackle four or five times around the base, each wrap below the last. Then hold up the wrapped hackle at the front and secure with several tight turns, trim any excess and whip finish.

To complete the pattern, first trim the underwings level with the bend of the hook. Then separate the butts from tips of the hair and trim level with the rear of the hook eye. The tips can then be stroked down to angle them back slightly. A drop of head cement on the hook shank under the hair will secure everything.

While initially tied to imitate a spent adult caddis, the success of this pattern during various stages of the hatch has seen it used more widely. With the sunken rear abdomen and split wing providing a suitable footprint on the water, it also passes as a mayfly emerger, while being ‘buggy’ enough to find success as a small terrestrial. Definitely a pattern worth remembering if you find yourself searching your fly box after yet another refusal.