I am sure those of you crazy enough to venture in to the tundra recently (I most certainly was) had a few bright flies with you. All year I try to fish imitatively, well almost, with drab browns and olives being wrapped around hooks to give some suggestion of life. However when that thermometer plunges and my mind turns to winter grayling I break out the flash.
Anecdotally the evidence seems to be there, most of my grayling recently have fallen to the above pink grub and it could not be much brighter. The flash in the abdomen is enhanced by wrapping the semi translucent material over a layer of silver tinsel, the photo does not do the effect real justice so you will have to trust me. Most of my friends have been doing the same as well, luminous Czech nymphs, tinsel jigs, hot spot pheasant tails the list goes on.
This got me thinking, are we catching more fish on bright flies because we are fishing mainly bright flies, or is there something more to this… my research seems to suggest there may be but I am not sure I understand it.
During the summer trout eyes detect light mainly using a pigment called rhodopsin and have low levels of a second pigment called porphyropsin. In the winter the ratios are flipped, the flip occurs due to changes in both temperature and shorter daylight hours. Interestingly it also occurs in salmon and seatrout as they prepare to enter freshwater again.
All well and good but what does it all mean Basil, well I am not sure. Porphyropsin absorbs light at a longer wavelength than rhodopsin, the highest sensitivity for rhodopsin is in the blue/green area and this shifts more solidly in to the green area. This also means that in the winter fish eyes should be more sensitive to red (and therefore pink) light and less to blue. Could this be the reason for the success of pink and hot orange flies in the winter? I don’t really know. All I can say for sure is for the next six weeks there will be a lot of pink on my leader.