One advantage of living by the side of a river is that you can get out at all times of night and day to "see what is going on". This evening is no exception. The river is not alive with rising fish as it can so often be. However, there were still plenty of rises to look at and to puzzle over as to what the fish were eating. This is a useful exercise in that it helps you to understand what is happening on similar occasions when you are there with a fly rod in your hand.
I watched some rises very near to the bank I was on and first impressions were that there were at least four fish rising very close to each other. This should make you ponder straight away. Trout dislike each other and will only tolerate each other, when feeding, if there is a very large amount of easily consumed food around. Might this be a pod of grayling, which are shoal fish and enjoy each other's company? Well it is unlikely, as grayling usually rise from near the bottom of the river to the fly and then they go back down again, to rise again a few moments later if they are in a feeding mood.
These rises were being made at a rate of about 15 to the minute. That's a lot! They could not be made by grayling. The rises were different from the spinner rises in that the fish was hanging in the water at a steep angle that made the neb, when observed from downriver, appear like a triangle or wedge shape. In this rather dark photograph (it is night time after all) you can see that there has already been one rise immediately in front of this second rise, where the camera has luckily caught the neb above the surface for a moment.
Now this seemingly crowded bit of water raised my curiosity so I sneaked up river until I was level with the rises. What a surprise! All the rises were being made by one trout! It was not still for more than a second at any time. Left, forward, right, drop back, forward, forward again, to the right, to the left, drop back, drop back some more, sip, sip, sip every time. The trout made each rise from directly under the midge it was about to eat. It spent its time just under the surface and tipped up at the angle you might just be able to make out in this even darker photograph.
Could I detect it was eating midges from the rise forms? Not really, it was a slight clue but could easily have been aphids, reed smuts, or some other fly. No I only know it was eating midges because when I got really close it was possible to see the midges on the surface and watch them being sipped away by this very active wild rainbow trout. But, next time I see rises like that, I will be trying an attempt at a fake midge and carefully checking just how many fish I am going to be trying to cast to.