Alan, chironomid fishing can definitely be daunting when first trying to figure out how to fish them effectively, but more often then not, they are the primary food source for stillwater fish and thus present a larger “window of opportunity” for the stillwater flyfisherman. As such, it pays off big to learn how to fish them.
There is a lot of information on this topic in the form of books, videos, internet, etc. (Brian Chan has a lot of good material out there as do others) that can be a big help and if you are serious, you should look into acquring these resources. Above all, commit yourself to fishing chironomids no matter how little success you may experience initially (there is no greater teacher than personal experience).
With that, the first thing to understand is the life cyle of a chironomid (egg, larva, pupa, adult) and the characteristics of each. Generally, most discussions involving chironomids and flyfishing is focused on the pupal stage, but I would first pay attention to the larval stage. In this stage, the chironomid resembles a worm, often called a “bloodworm” by fly fisherman because of the maroon or red coloration of the natural. Chironomid larva can be found in other colors, such as brown and olive. Generally sizes run from 8-16, but I have had great success fishing imitations in the 8-12 range.
Chironomid larva live in tubular homes on the bottom of the lake at various depths depending upon the time of the year. Spring and late fall are particularly good times to fish larval patterns because these times mark their seasonal migrations to shallow (spring) or deep (fall) water. During these periods, larva will leave the security of the tubes which encase them and migrate to shallower or deeper water. They are extremely poor swimmers, and at best wriggle and writhe their way near the bottom, completely at the mercy of the elements, but more importantly the trout as well.
Periods of low light are also effective times to fish chironomid larva because they will leave thier tubes under the security of such conditions to feed on the available detris and vegetation. When fishing larval imitations, it is best to fish them 1-2 feet from the bottom (although there have been a few instances when fishing them higher up in the water column has really been effective for me when I could not elicit strikes fishing the same pattern near the bottom; I am not really sure why though). Key to fishing larva imitations is giving them some slight movement (although this is often conditional depending upon the fish; they may want it dead still some days) every so often. I have had many fish immediately strike my imitation after giving it a quick, subtle twitch following a period of letting it remain motionless. One needs to experiment with retrieves when fishing this stage of the chironomid (something which is true of the pupal stage as well). This is also a good stage of the insect to fish when there is no noticeable hatch going on as larva are available year round to trout.
The most commonly fished stage of the chironomid is the pupal stage. It is from the pupa that the adult eventually emerges on the surface, although this process takes a long time because pupa ascend to the surface VERY slowly (something critical to flyfishers as we try to imitate the pupal ascension with a retrieve that mimics the natural). Initially, pupa will stage themselves near the bottom before beginning their ascent to the surface (this staging can last for a few weeks), and trout will feed on pupa near the bottom just as they would a larva. After the pupa begin their ascent, the trout will follow them upwards as they rise to the surface, meaning that trout can be feeding on pupa at any depth within the entire water column from top to bottom.
In light of this, it is my opinion that the most important general factor to consider when fishing pupal imitations is depth. As I mentioned, fish may be feeding on pupa at different depths within the water column depending upon the progression of the hatch. As such, to be successful, an angler needs to put his fly where the fish are feeding. As a general rule, I will start fishing the bottom of the water column by keeping my fly(or flies) 1-2 ft from the bottom. If that does not work, I will make depth adjustsments upwards in 2ft increments as necessary (it is important to note that fishing the bottom two feet in 10 feet of water for example may not produce fish while fishing the bottom two feet in 20 ft of water will produce fish; sometimes you need to change not the depth of the fly you are fishing, but the depth of the water you are fishing in). If you can, I’d fish a two fly rig with my top fly about 12-18 in from my bottom fly (use fluorcarbon if at all possible).
Two other important factors that fish will key selectively in on at times is size and color. Though this is not always the case, it is sometimes necessary to fish an imitation the same size as the natural the fish are selectively feeding upon (however, sometime during a very heavy hatch, it pays to fish a larger imitation to make your pattern stand out from all the naturals; this has often worked for me when fishing an exact sized imitation did not). To determine size and color, you can use a stomach pump or capture a natural pupa from the water with an acquarium net. You can also look for shucks floating in the water to get a read on size, or capture an adult (the pupa is often one size larger than the adult). The adult is usually a lighter shade than the pupa, so use a slightly darker pupa imitation. Important to note is that there often is more than one size and color of chironomid hatching and/or available to trout in many lakes, so one needs to be consistently observant and flexible in their approach, especially if fish are feeding selectively.
As I mentioned earlier, the pupa rise very slowly so the retrieve you employ must match the ascent of the natural. A figure 8 retrieve that can take upwards of five minutes to get to the surface, depending upon how deep the water is, is not uncommon. The type of retrieve employed is relative to the situation and conditions, specifically what the fish want on a particular day. Sometimes they want the fly with no movement, or quick, subtle movement, or steady slow movement, etc… It pays again to be flexible and mix up your retrieves until you find one that the fish want. Do not be afraid to go against the book and fish the chironomid slightly more agressively than one would typically think to fish it in light of how slowly the natural ascends to the surface. Some days, for whatever reason, the fish respond to a more agressively retreived chironomid (not that you are fishing like a streamer mind you).
Another thing to consider to location. Do not keeping casting to the same areas, especially if they are not producing. Sometimes simply casting a few feet to the right or left of an unproducing location will bring about a strike. There are some days when I will only let my fly sit in an area for thirty seconds or so before picking up and casting to a new location. That alone has caught me fish when changing patterns, fishing depths, etc. has proved unsuccessful.
There is so much to this technique, but I have gone on too long already. It is somewhat of a passion of mine so I apologize if I bored you with too many details. If there are any questions you have, please feel free to email me at dkutt69@hotmail.com and I will help you in any way I can. Good luck.
Dave