Yeah, for sure it is an unlimited amount of fish in a stocked pond.
My suggestion for you in stocking ponds is this (I had a fisherman who did this and made $500,000 easily).
1) Create a pond
2) Buy loads of cheese at the general store
3) Use your cheese to catch ten alley catfish and stock your pond with them
4) Catch a bunch of alley catfish from your pond
5) Use your alley catfish to catch ten angelfish and stock your pond with them
6) Catch a bunch of angelfish from your pond
7) Every night, catch three deathfish until you have ten of them and stock your pond with them
Now, assuming you have cheese, you never have to leave your house to make tons of money. Just make sure you have enough angelfish to catch your deathfish, and you can easily spend all day catching deathfish.
I love this because there is no time limit. And there is no catch limit. At the graveyard, you can only do it at the middle of the night and can only catch three per night.
Try this. Make so much money off it.