Forget the camera for now. Let’s just look at composing a picture in the countryside.
Here we are experiencing the river running as a relatively thin thread through beautiful countryside. The angler is far off, and barely visible. He is diminutive in the large landscape, and that landscape is wide open, and it’s vastness is evident:
In the picture above we lose the sense of high mountains. We cannot fully appreciate how high they are, and the degree to which they dominated the river valley that lovely morning. To achieve this, try orienting the picture the other way. In other words take the shot with the camera held sideways:
This also makes the river more significant, and focuses ones attention on matters piscatorial somewhat more than the picture that showed more countryside.
Then to get a sense of the river channel, and the focused angler way down there, immersing his experience in the narrow river channel itself, with the high mountain behind, simply zoom in: