So... how does fishing work?

[Falaris]

If you don't deplete a fishing spot, does it slowly regrow?

Does it slowly regrow if you don't deplete it?

How about resource dredging?

I have my theories, of course, but I don't know if they're correct. The game seems to hint that depleting a source WILL destroy it. You even get an achievement for it.

[Patton Plays]

I've depleted entire spots on the map and they have always returned. Resources seem limited.

[Keysmash666]

Resources are infinite, they just take a very very long time to respawn

[RequiemsRose]

For the most part, everything will respawn if given enough time. Some of the exceptions may include spoilers though. Without spoilers, the only ones that don't seem to respawn eventually is the dredge spots for research parts (though the regular resources will respawn and you can sometimes find research parts in those to)...oh and obviously the unique quest related items won't respawn either, which can be unfortunate in some cases if damage to your boat causes you to lose the related item.