Daunya, I've been looking for the same thing for a long time now, and the kinda-sorta rule of thumb is to take the minimum level of mobs in the zone and multiply by 5 to get your minimum cast skill, and multiply the top level mobs by 5 to get your "no-miss" skill.
That said, there are several zones that fall outside of this rule, such as Winterspring, Plaguelands, Azshara, and Zul'Gurub. I haven't been to any other zones that require uber fishing skills, although I think that Moonglade may be on that list too. I'll play around with my fishing gear tonight and see if I can't get the minimum cast skill range in those zones to within 3-5 points.