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[Dame de la Licorne]

Hi all!

So I'm building a fort on a map where the only fish present are in the caverns.  I recently appear to have removed all fish from one of the cavern lakes (and haven't started fishing in the other caverns yet).  My question is this: is there any way to restore the fishable-fish populations once they've been fished out (DFHack's region-pops boost doesn't seem to do it)?  If not, is there any way to achieve sustainable fishing?

- Dame de la Licorne

[Loci]

DFHack's region-pops boost doesn't seem to do it

Not too surprising; region-pops boost is a *multiplicative* change--zero times anything: still zero. Try region-pops incr instead.

[Dame de la Licorne]

Using region-pops incr (using FISH_CAVE and 10), then applying a boost factor greater than 1 still results in the cavern fishing zone displaying (0) fishable tiles (there are (2) water-source tiles).  Region-pops also says that there are 30,000+ cave fish on the map, so I'm assuming those numbers are for the unfished lakes in the other caverns?

- Dame de la Licorne

[PatrikLundell]

It's a known issue that fishing sources can get depleted. I've heard conflicting information regarding whether they can be restocked by themselves over time, or whether they remain depleted, however.
I suspect region-pops would be of no help, however, both because cavern fish are vermin (and thus don't migrate like "real" animals do), and because fish availability seems to be a property of 16*16 in game tile regions, rather than regional availability (like other caverns up to 6 world tiles away, not only those in your embark).
I don't know of any tool to "adjust" fishing sources, though. The safest is probably to reduce fishing while there is stock, although I'm not aware of anything indicating whether the stock is in danger of being depleted.

[Dame de la Licorne]

Got it.  That was what I was afraid of.  I'll be more conservative with my fishing in the other two caverns, as my question was more in line of trying to prevent fishing depletion there.  I kind of assumed the current cavern was irrecoverable.  Thanks!

- Dame de la Licorne

[Miles_Umbrae]

You could always copy the save-files, turn off all fishing skills, and let the fort run for a few years and see if they replenish.

[Loci]

Using region-pops incr (using FISH_CAVE and 10), then applying a boost factor greater than 1 still results in the cavern fishing zone displaying (0) fishable tiles

Your dwarves don't automatically know that fish have magically appeared. Zone "fishable" tiles are reset occasionally (seasonally or yearly, perhaps), at which point your dwarves will again try to fish the lake (assuming you haven't disabled it).

[Dame de la Licorne]

Ah, I did not know that.  I'll keep an eye on it.

- Dame de la Licorne

[mikekchar]

I've noticed this is somewhat true of herbalism gather zones as well.  If you set a zone, the dwarfs will go and pick up whatever they can find.  They *will* return eventually, but not necessarily in an optimal fashion.  If you remove the zone and reset it, then the dwarfs will again go to pick the area clean.

[NTJedi]

My river freezes for two seasons out of the year... so I'm guessing the freezing kills the fish and thus killing my fish population.     

[PatrikLundell]

I don't think freezing affect vermin fish (you obviously can't fish while it's frozen, but since vermin fish aren't real creatures, they probably can't be killed by freezing). It does kill "real" creatures, including larger fish, though.

On the original topic:
As far as I can see the DFHack structure is missing information relating to vermin "fish": There's a structure for the physical outer bounds of murky pools (but not cavern lakes), but nothing else about the bodies of water, such as the fish population state. Since you can deplete one pool but still have fish in another, there ought to be some information on what's available where that hasn't been mapped (or I've failed to locate).
A data piece that might be relevant to the OP issue is that there's a structure for Populations on a world tile and layer level (with each cavern being a layer), and that structure has an Extinct flag, which may or may not be relevant for vermin fish. However, when I looked at it for a cavern of my fortress the cave fish number was finite (as opposed to many vermin that are innumerable).

[Dame de la Licorne]

However, when I looked at it for a cavern of my fortress the cave fish number was finite (as opposed to many vermin that are innumerable).

Should this be posted as a bug, then?

- Dame de la Licorne

[PatrikLundell]

I wouldn't consider over fishing to be a bug. Not replenishing fish in bodies of water connected to the outside (rivers, the ocean, cavern lakes with edge access) over time would be a bug (and some reports say that happens). It makes sense that intense fishing would deplete a small isolated body of water, but it would also make sense that the population should recover from fry eventually (abstractly, of course). Not being able to (re)stock bodies of water with new fish is more of a missing feature than a bug.
It seems DF keeps track of the vermin fish population of each body of water separately, but we just don't know where that info resides.

It can be mentioned that I fish only to get shells in a mood emergency, as I generally have more trouble using up the food generated than to feed my dorfs (my obsession with trying to stock the fortress with every kind of booze known to dwarf may have something to do with it), so my bodies of water are in their initial pre fishing state.

[NTJedi]

I wouldn't consider over fishing to be a bug. Not replenishing fish in bodies of water connected to the outside (rivers, the ocean, cavern lakes with edge access) over time would be a bug (and some reports say that happens). It makes sense that intense fishing would deplete a small isolated body of water, but it would also make sense that the population should recover from fry eventually (abstractly, of course). Not being able to (re)stock bodies of water with new fish is more of a missing feature than a bug.
It seems DF keeps track of the vermin fish population of each body of water separately, but we just don't know where that info resides.

It can be mentioned that I fish only to get shells in a mood emergency, as I generally have more trouble using up the food generated than to feed my dorfs (my obsession with trying to stock the fortress with every kind of booze known to dwarf may have something to do with it), so my bodies of water are in their initial pre fishing state.

I would think this is a bug since dwarves fishing with fishing poles doesn't sound like a logical path to cause fish for an area to go extinct.  Now if the dwarves were dragging fishing nets across the bottom of a majorify of the river for five years then I could understand the fish vanishing.

[feelotraveller]

,,,dwarves fishing with fishing poles...

Never seen a fishing pole in an inventory, or a fish net for that matter.  Best I can tell dwarfs fish like bears, although there is rampant speculation that beards are involved somehow.