Flyfishing - Sinking Flies

When I started fly-fishing there was only one way. We used a floating line with a three-metre monofilament cast (tippet) which had two droppers so we could fish three flies. They were small (size 12 or 14), slim winged and tied ‘sparse’. That was the way you fished in Scotland, by golly, and heaven forbid you should offer any variation. People did, of course. Some fished four flies. Others, in more outlandish places, used larger, more hairy versions. So far as I know all these methods worked.

There were quite a few occasions when we had three fish on at once and many more when we had two of the spotted beauties pulling hard for survival. Fortunately, they mostly weighed under 300 grams, so we weren’t broken very often, even when they tried pulling in opposite directions.

When we started to fish in the English Midlands the word ‘nymph’ entered our lives. Jo became an ace with a size 12 Pheasant Tail during the chironomid hatches which often lasted a whole day on those lakes. We caught many a limit bag of fish up to two or three pounds. Using a single fly of course.

But the real awakening came when we began to realise the truth of the old axiom that trout get 90% of their food from below the surface and started to fish deep on days when there wasn’t very much action near the surface.

One day we fished in a qualifying oompetition when absolutely nothing was happening at the surface. On went the new Wet Cel with a 12-foot leader tapered to four-pound breaking strain and I started counting down before retrieving.

Twenty seconds, very slow retrieve . . . nothing. Thirty seconds . . . nothing. Forty seconds . . . same. Fifty seconds . . . bump, bump and I was into a strong fish which created a lot of concern on my part before it came to the net. Four more followed it into the net at intervals that afternoon. There wasn’t half a pound between them and collectively they went just short of 18 pounds.

I finished with possibly the heaviest bag but didn’t make the team because some of the ‘guns’ hooked into a shoal of newly-stocked 14-inchers and got their nine-fish limit bags. The team was picked from those who caught most fish.

Although I didn’t achieve representative status I learned a lesson or two about catching trout that day – the most important being that I had to buy a Wet Cel for Jo pdq.
Since then I have probably fished as much with a sinking line as with a floater. Though I much prefer fishing with a floater (and a dry fly if possible) I have no doubt that fishing below the surface produces more and better fish in the long run.

So what are the options? Deep, deeper, deepest.

In the early days of PVC fly lines there was very little standardisation of sink rates. The only sure thing was that a 12-weight line would sink faster than a 6-weight of similar construction. All that has changed with modern manufacturing methods. It is now possible to buy lines which not only sink at guaranteed rates (within a small range) but where each line in the category sinks at the same rate, i.e. a 6-weight fast sinker will hit the bottom at the same time as a 12-weight.

In addition, we can now buy sinking lines which are guaranteed to sink tip-first. Until density compensation was introduced, the tippet end lagged behind the belly of the line, so, at the extreme, the fly was often fishing many feet higher than the belly.
The upshot is that we can now say with some certainty that after ‘x’ seconds the fly will be at ‘y’ metres below the surface.

Some line manufacturers indicate the sinking rate of a line with a number. Airflo is one. In their system, zero means floating; 1 means intermediate; 24 means that it sinks like a depth charge. Any number in between means… in between. The good thing about it is the standardisation: lines, leaders and line extensions with the same number sink at the same rate. Vive la difference
Why different sink rates? Isn’t one enough? Well, yes it is, provided that you are always going to retrieve at the same rate and have time on your side. As we have already seen, the depth at which your line fishes involves two factors: the sinking rate of the line and the speed of the retrieve. You can fish 30 centimetres down by using a slow intermediate line which has been allowed to sink for 20 seconds and is retrieved slowly, or you can use the fastest sinking line retrieved immediately at warp speed.

Obviously, if you want to fish a nymph at a depth of five metres you can use a slow intermediate which will take four to five minutes to reach the required depth. On the other hand, you will probably wish to use a fast sinker which will get there in 50 seconds. You may think that there isn’t a great deal of difference between a flyline sinking at eight seconds a metre and another which sinks at six seconds a metre. In fact the difference is 25% – if they are retrieved at the same speed. the faster sinker will fish 25% lower.

Another consideration is that retrieval will, sooner or later, cause the line to rise in the water. The extreme example is where you cast a fast sinking line into deep water. If you are fishing from a stationary boat or from shore, and you don’t strip off more line as it sinks, the fly will eventually hang almost vertically below you if the water depth allows. In that case, your first pull will lift the fly.

A similar case occurs when fishing with a floating line. Your nymph will sink under its own weight, as will a monofilament leader and tippet, but the retrieve will sooner or later cause the nymph to rise – later if you retrieve very slowly.

To summarise: If you want a fly or nymph to fish at depth for a longer period, it is necessary to use some sort of sinking line and leader. And the depth at which you want to fish is controlled by the sink rate of the line and the speed at which you retrieve.