okay so question why do i get poisoned by what seems like a splash potion is there any way for me to catch it instead of me getting poisoned? and why does that happen??
This is happening because you or the server you're on is using a plugin. I don't know which one from mind though. It is not common vanilla behavior.
The plugin enhances drops which you get from fishing, but it also adds a few extra negatives such as poison splash potions as well as triggered tnt.
Found it, this behavior is introduced by mcMMO, see here, it's a plugin which is pretty common on servers. Doing a decent amount of fishing myself I seriously disliked this craziness so I turned it off on my own server.