I used to like to go out on the bridge several times a day. I would stand on the cafe platform and stare into the water, lost in my thoughts. One day in high summer, I noticed there were thousands of little fish lurking in the shade provided by the bridge and the platform. I also noticed that the sun was at such an angle it cast a shadow of my upper body onto the water. And then I noticed the little fish were moving into the shaded area provided by me.
So, here's the confession; I would wait until my shadow was full of fish. And then I would deliberately move several steps to the left or right, thereby exposing the fish to the full heat of the sun, causing stress, trauma, and goodness knows what else to the poor little blighters.