Finding a fishing spot, the bigger the better?

[Allen]

So the handbook says you should fish in 'fairly large' bodies of water because small ponds likely won't have fish.

Is this simply a demerit for small bodies of water i.e, as long as it's bigger than a certain size it doesn't matter how big it is-

Or is there a bonus for bigger bodies of water i.e, a bigger lake/sea is always better?

[Averixus]

A pond less than 100 blocks in volume will never give a catch from the "invisible stock". A body of water 1,200 blocks or more in volume will always have the maximum abundance of "invisible stock" (taking into account other factors like local fish distribution, depletion, etc). The abundance will scale between those two sizes. 1,200 blocks in volume is not very big - that's a pond which is 3 blocks deep and 20x20 across. So any bigger than that makes no difference.

Abundance determines both how long it takes to get a catch, and how likely that catch is to be adult or juvenile. Although there's currently a vanilla bug that higher abundance gives more juveniles instead of more adults, so if you're playing on vanilla and specifically want adults at the expense of catch speed you might want to fish in smaller ponds?!

(Little plug for the mod I just released, which fixes that bug along with a few others - https://mods.vintagestory.at/fishingconfig)