I created a new map and can't seem to get Tuna to show up. I have varied my under-water levels and I get Anchovy as the major type and I have plenty of Shellfish, though not necessarily in the more shallow waters which would seem more logical. And, as it should be, I have salmon appearing where water currents are strong, mainly in rivers, but for some reason I have no tuna at all. I tried changing things on my map, but I still don't get tuna fish to appear. What are the rules here? I have done several searches here and online to find this answer and I'm either not getting the correct key-words or no one really knows.