On a "normal" map, if there is such a thing, where you expect to see Ice terrain near the far north and far south of the map, you'll be more likely to find Crab Resources closer to the poles, transitioning into Clam Resources closer to the more central latitudes.
Fish Resources not not seem to be affected by latitude and will appear at pretty much any latitude.
I'm pretty sure that Crab Resources and Clam Resources generally (always?) are Coastal Resources, while Fish tend toward being Ocean Resources, although you can also sometimes find Coastal Fish Resources (dubbed "Magical Fish" Resources due to them provided the same +1 Commerce that Coastal Crab or Coastal Clam will provide but providing an additional +1 Food on top of what Crab and Clam provide).
As an example, I just generated a map and in the southern hemisphere, I had Crab on one square and Clam on the square 1N of there. Since Fish can and will appear in any latitude, it should not be too hard to believe that a Fish Resource could feasibly fall in the same big fat cross as that Crab and Clam.
Also, the map generator will add Food-based Resources to most players' starting spots (including the AIs' starting spots), so a player starting near the Crab + Clam start might get a free Fish Resource tossed in without help from a Map Maker, as one example.
Whale Resources will also tend to appear closer to the poles, as will Fur Resources, Silver Resources, and Deer Resources.
Certain Resource types generally don't appear on certain terrain types... I don't recall ever seeing Ice Horses (just Ice Archers, for those in the know), nor do I recall seeing Plains Hills Horses. I also don't think that I've seen Desert Horses.
But, different map types (the Fantasy map script comes to mind) and different climate settings (Temperate, Tropical, Arid, Cold, etc) can also alter the balance of Resource distribution.