How can I quickly stockpile bait for lava fishing?
The spawn rates of critters are affected by things like Water Candles and Battle potions, so by using either of these you can speed up the gathering of them.
This does have the unfortunate side effect of also increasing enemy spawn rates, so if you’re worried about danger this may not be ideal for you.
I would recommend using potions such as water walking or obsidian skin to make your life a bit easier in the Underworld. But, there is no real easy way to stockpile these critters.