I was thinking about describing "why" a fish takes a certain fly. In fact, first I was thinking how to desribe the decscription. so to speak. Becuase one has to be really care in selecting words. The fish takes the fly becasue it thinks... Full stop - fish don't think (I think).
So in order to concentrate my thoughts and arguments, I thought about the fly in the PoD - the FlashBack Nymph, which I've written about before, not least because it's one of my favourite searching nymphs. I was tying a new batch, and that was really why I started thinking about this subject. Because this fly works everywhere and at any time during the year - but why?
So - why does a fish take a fly?
Basically, the fish's instincts trigger the fish to investigate whether or not it's edible. Based on the number of fish I've caught on the FlashBack Nymph, I'd say this fly does well in triggering that instinct.
The interesting discussion is, of course, how many triggers and how precise they need to be to cause the fish to "investigate". Selectivity is interesting in this regard, because when a grayling or trout is locked onto a certain insect - sometimes even onto a specific stage in this insect's life, all flies won't work - no matter how they fish in other situations.
A trout keyed in on a specific mayfly's emergerstage won't take the FlashBack Nymph - mainly becasue it probably doesn't really see it. The fish has it's attention turned towards the surface. I haven't tried presenting a keyed-in-trout for an unweighted FlashBack, but I've seen enough keyed-in trout and grayling to know that only very few would accept the offering.
In these instances a specific and very precise imitation is rarely necesssary, but it's important in my experience to have a fly that has some level of imitation. Dave Whitlock has prioritised elements of a fly and it's presentation in this way:
Within this heirarchy any fly can be impressionistic, realistic or exact. The problem in this lies in telling what exactly "seems" for instance realistic to the trout. Maybe a scruffy thing like the FlashBack seem more "realistic" than an exact, superrealistic imitation?
I think I more or less agree with Whitlock's 1-5, although I think that maybe there should be no 5, and two 4's, so to speak (sorry dude) - in some instances colour really matters, and maybe it should be even higher up?
I'm not really sure where I'm going as you can maybe tell, but it's fun thinking aboout, and I suppose the old cliché that the fish is the final judge really is true. It's fun fishing imitations to keyed-in trout, almost knowing the the fly you've tied and knotted onto the leader really does resemble the insect the fish is keyed in to, but really, it's enough that the fish thinks (there, I said it) it needs to investigate and take the fly into it's mouth, offering me a chance of hooking it. Although - I do think that there is actually a difference in the way a fish "takes" a fly - whether it does it to investigate, or because it simply knows (I know, I know) that the fly's food. I firmly believe that there's a better chance of hooking it in the latter case. The problem is telling if there's really is a difference...
I'll finish on a more concrete note. The reason I sat down to tie new flies was that I'd ordered some new dubbing. I'd come across Andrew's Scruffy Dubbing several times on Facebook. I thought it looked quite interesting and I decided to order some. The delivery came fast and the dubbing is really nice. They're all blends - some of them of quite a few colours and I think there's a little synthetic in it as well (not sure). The blends are really nice, well well blended, no lumps, and everything seems very well handled and cared for. It dubs extremly easily and goes on equally well tight as it does loose. It brushes out well. Check out the PoD - the dark thorax really consists of a number of colours. It's (mainly?) natural, so the colours will of course darken when they're wet, so remember to take that into account if you order some. Enough said - if you're tempted, the dubbing has my recommendation - I really like it.
Thread: UNI 8/0, tan.
Hook: Ahrex Freshwater FW 540, 10-16.
Back: Pearl flash.
Rib: Chartreuse wire.
Abdomen: Caddis Green Andrew's Scruffy Dubbing.
Thorax: Sooty Olive Andrew's Scruffy Dubbing.
Head: 2,5mm tungsten bead.
Have a nice weekend!