My Grandfather described to me how to guddle for trout and I’ve used the technique several times. I learnt in the burn which is close to the house I grew up in, and forty years ago it was full of minnows, stickleback and brown trout. Then a business upstream had a chemical spill and they all disappeared.
I learned which rocks the trout would lie under or against, tickle their belly and then either slip a finger in the gills or just throw them up onto the bank.
I also caught a salmon using a rabbit snare in Alaska once, but that’s another story…..