KEY POINTS:
The river is low and clear on a bright sunny day. You are using exactly the same small natural flies as the angler fishing nearby. He's catching plenty. You're getting nothing.
Chances are he's using a fluorocarbon trace, which is less visible to the fish than your traditional nylon monofilament.
Fluorocarbon lines were developed in the 90s by the Japanese for use on their tuna longliners on bright days. Their catch rates immediately went up, and they found that the line, as well as being less visible underwater, withstood greater abrasive shocks than mono, was not weakened by strong sunlight and had a longer life.
Since then manufacturers have been climbing on the fluorocarbon bandwagon and many brands have reached the market, targeting easy-to-catch anglers with claims of "stealth characteristic", "invisibility", "shock absorbency for fighting power" and "low memory formula".
Although it was developed for seafishing, the troutfishers in this country have made it their own, and some serious fishers have now abandoned monofilament altogether. Anglers don't need much convincing to take on board anything that suggests they'll catch more fish.
I have been testing various brands and strengths of fluorocarbon for the past year and have concluded:
* We've come a long way since we used traces made of cat-gut that had to be soaked overnight to soften them.
* Fluoro is almost invisible underwater because it has almost the same light refraction rate as water, so it "disappears" when submerged.
* It catches more fish in low, clear water than mono, which is highly visible to a trout in such conditions. Some fluoro has a smaller diameter than mono of the same strength.
* Fluoro has greater knot strength than mono, and it doesn't matter which knot you use as long as you tie it accurately and cinch it firmly with a slobber of saliva to prevent burning.
* Fluoro has greater abrasion resistance. A fish can bend the line round a snagged branch or rock without breaking it.
* Fluoro does not weaken and stretch like mono. But mono, because it stretches, might endure more weight.
* Fluoro sinks rapidly to get nymphs down more quickly, whereas mono will lie glistening like a warning beacon in the surface film.
* Generally, I have found fluoro superior to mono on all fronts, but it is not necessary to use it, except in extremely clear, low water.
Fluorocarbon has one big disadvantage: price, which has not yet come down despite the number of brands competing for anglers' attention in the past two years.
A 50m spool of fluoro sells for between $27 and $30. A 50m spool of mono is $5.
Anglers can avoid using such expensive material for the whole trace by tying only a short piece of fluoro to the end of a mono trace with a blood knot, and again between the two flies.
Not everybody is a fan of fluoro. Prominent angler/writer Hugh McDowell, in a recent issue of Troutfisher magazine, writes: "I don't use fluorocarbon, period. During an entire season's experiments I never encountered a single instance where a trout that had refused a pattern on regular mono took it when presented on fluorocarbon, despite what the marketing boys claim."
He's got a point. Where was fluoro when we had all those great catches years ago, even in clear water on bright days? Where was fluoro when the early Tongariro anglers caught trailer-loads of trout between 3kg and 7kg on cat-gut?
But fluorocarbon is certainly superior. It has its place in gin-clear water where it is more likely to be successful, or in deep pools and currents where the angler needs to get flies to the bottom quickly. And a dry fly tippet of fluoro will sink and not require degreasing, as with mono, to stop it sitting in the surface film, where it is easily visible to trout.
But despite the advantages of fluorocarbon, on most occasions monofilament will do the job perfectly well - at least until the fluoro prices come down.
