The Rise: What can we learn?

I am new to trout fishing. The last two weeks I have been exposed to two different trout rises and takes. Neither time have I been able to observe what was on the water. Little brownish flys were in the air.

The first week I what I would describe as a ballistic rise (take). It was if rocks were being thrown in the water. Very large splashes and loud noise in the water were this rises trademark.

This week the rise was that of whale scooping up krill. The fish came to the surface with its mouth open, dorsal and tail fins above water. It would stay above water briefly and then quietly submerge. Again I did not see anything on the water but there was a cloud of flys above.

My buddy says it is different stages in the fly life cycle and I would agree, but what stages. Any help/comments are appreciated.