Chironomid adult, pupae and pupal shuck
The Chironomid is a staple food source for the rainbow trout in most of the interior lakes of British Columbia. The insect is available year round in three of it's four life stages, but nothing gets the rainbows going on a feeding frenzy like the chironomid does when it hatches from a pupa to an adult.
The Chironomid Life Cycle
Many species of chironomid live in the muddy bottom sections of the lake. The chironomid does a metamorphosis from egg, larva, pupa and adult to complete it's life cycle. The insect starts out as an egg that is laid by the adult fly on the lake surface. The egg sinks to the bottom and after a short period hatches into a larva or bloodworm. The bloodworm is characterized by the red hemoglobin it is named after. The larva burrows in the soft lake bottom mud forming small tubes where it will live feeding on detritus and other decaying matter until it is time to pupate.
Photo: Dale Sharp
Larva or Bloodworm
The larva or bloodworm can be found in colors of red or green. They can live in very deep water and low oxygen environments. The bloodworm is an important food source to many bottom grazing trout, especially during the winter months and early spring, as well as the late summer months when the surface temperatures get too warm and the trout seek shelter in the depths.
Once the bloodworm decides it is time to pupate, determined by water temperature, it closes itself off in it's lake bottom tube and transforms into a pupa, much like the caterpillar in the cocoon that morphs into a butterfly. Once the pupae have fully developed they will wiggle themselves free from their tubular cocoons and ascend to the surface in mass to hatch as adult flies repeating the process all over again. It is this ascent to the surface that really triggers the trout's appetite. Rainbows will literally gorge themselves with these succulent little morsels until their stomachs are stuffed full.
Chironomid pupa
There are many different species of chironomids in our lakes, but most colors observed are shades of green, black, red and brown. Samples taken indicate the green chironomids are usually the smallest and the most abundant. The largest chironomids are refered to as bombers and are usually in color shades of black or with red and brown, but they can be many colors and color specific to individual lakes.
Chironomids come in shades or combinations of green, black, red and brown
Recognizing a Hatch
When fishing for rainbows with a chiromonid pattern, look for the telltale signs of the pupal shucks littering the lake surface. The shuck resembles a tiny transparent carrot shaped tube. If a hatch is occurring the adults can be observed splitting out of their pupal shucks and momentarily sitting on the water's surface to dry their wings in preparation for flight and mating.
Adult chironomid emerged from it's pupal shuck
Watch the lakes surface for rising fish feeding on or just below the surface. The swallows also feed on the adults and can mark a hatch as they swoop the lakes surface to feed. They actually hit the water, I think plucking the pupae from the water as well as the adults.
Rainbows on the rise during a chironomid hatch
The hatches start to occur a week or two after ice off. As the spring progresses the hatches will intensify as the water temperature increases. The chironomids will hatch in lesser numbers right up to ice on.
Flyfishing Techniques
To fish this exciting food source, one technique is to use a floating line with ten to twenty-five foot leaders and a strike indicator to hang the pattern just above the lake bottom. Occasionally when the hatch is underway, a fly need only be presented a few feet below the surface to entice the fish. As the season progresses anglers move out to deeper water. In the deeper depths a sinking line can be used to again dangle the fly off the bottom and retrieved very slowly to imitate the ascent of the rising pupae, this method can be exhilarating as the trout will just pound the fly, so don't leave the rod unattended. Another method is referred to as fishing naked, no bobber. Floating lines and long leaders are used to cast out the fly pattern, letting it sink to the desired depth and retrieving the fly very slowly, this technique allows for more area to be covered if the hatch is a little more sporadic.
Fly Tying
When buying or tying your patterns consider the use of silver or red tinsels for flash. Red will imitate the hemoglobin found in many species. When chironomids are ascending to the surface their body segments fill with air to aid in the upward journey. The air trapped in the body segments looks silver, using it in the pattern will add realism.
Air trapped in the body segmentations
The flies are quick and easy to tie in a variety of colors
Tiemco 2457 size 16-10
Tungsten bead
Gills (optional) antron or fluro fibre
Thread or floss body
Silver, gold or red rib
The Fish
This nice rainbow was caught sucking back my chironomid pattern that was suspended below a strike indicator in twenty feet of water, she put up a great fight with several good leaps and runs, she was gently release back into the lake, maybe a little wiser but none worse the wear.
A nice rainbow caught on a chironomid pattern
Give these fun and productive techniques a try next time out on your favorite lake, it might take a little moving around or a couple sessions to locate a hatch, when you find the chironimids the fish shouldn't be too far away. See ya on the lake.
Photos and text by Lewis Johnson © TheChronicFlyfisher.com