I think these are always great stories, I often think back to my first catches.
Unfortunately I can't remember my exact first fish as my father took me out fishing so much as a really young child.
What does stand out in my memory is my first real catches while I was fishing alone.
It was late fall at my cottage, a cold day with lots of rain. I was casting off the dock, I had not had a bite all day but I continued diligently casting as my hands froze. The lake is a clear rocky one and there's a drop off too a little over 25 feet a distance off the dock. I remember reeling in then feeling a incredibly jerk on my rod and complete surprise and horror. My cheap click pool was bent right over as I attempted to land what I was sure was a huge fish. The fight seemed to last forever and my heart was beating. Finally I brought to the dock what I know now was probably a 2 or so pound lake trout. I looked at it a while in the water not really knowing what to do with it. I attempted to lift it up by the line and pull it onto the dock....the line snapped and my heart dropped.
I then ran to the cottage and out of breath told everyone that I had "caught a huge silver fish". Nobody believed me and laughed. I believe it was on a mepps spinner.
Another time from my very young childhood stands out in my memory. Me and my brother would go down to a very small creek and fish for chubs and if we were lucky a small trout.
We ventured out one early morning in an attempt to catch a fish. Our rig was Simple, pencil with a length of mono wrapped around it and a small hook. We would catch a couple worms or my favorite, grasshoppers. We had grasshoppers that day, we found a spot and carefully hooked the grasshoppers. We would allow them to struggle as floating down the surface. On this particular day as soon as we plopped them on the surface a brown trout surfaced and took off with the hopper. The fight was intense as the trout darted for the bank and splashed on the surface. Before the morning was over we had caught 2 browns both about a pound and a half each. We ran up with glee to show our bad our huge fish.
Both of these sort of incidental catches really fueled my fishing at a young age.