Fish can be caught by a dwarf with the fishing labor enabled. Fish will be caught raw, and must be processed at a fishery before being edible. Fish can be a good food source for an early fortress, but larger fortresses should probably butcher large animals like whales or start growing their own food.
Small fish are treated as vermin, and can only be harvested by processing. They will not show up on the nit menu nor will they have any status when iewed. As such, it is difficult to know how many are on the map. However, if there are no small fish in an area, the game will announce it. Note that the vermin you can sometimes actually see seem to have no relation to what you can fish Verify; that is, if you see a turtle in a murky pond, that doesn't mean that you can get any turtles out of that pond with the fishing labor.
Larger fish, such as carp and halibut, are individual creatures that can only survive in sufficiently deep water (at least 4/7 or higher), and their corpses are butchered to become food, rather than processed. Larger fish, such as those stated above, can fall over in the water, stand in water, vomit in water, and kill a drunken stout fisherman (who is the only source of food in a early fortress) by making them dodge into the water when the fish decides to go after him.
Due to the relative ease at which fish can be acquired in the early game with a sufficiently skilled Fisherdwarf, fish are often a stable source of food for newer outposts which have not established a stable agricultural system yet. They are also an excellent supplement to any larder.
If you have a waterfall in your land, large fish may decide to jump off and commit suicide, so it is good to put a grate under the waterfall for fish to jump into, so that they suffocate, then you can butcher them for meat and bones, otherwise it is hard to butcher fish corpses.
- There are so few cave fish and cave lobsters in the world that you probably won't get any on your site. Bug:4505 This may be worked around by significantly increasing the [POPULATION] numbers for underground vermin fish in the raws to match above-ground populations; however, this requires regenerating a new world.