The level of the fishing zone does not determine whether or not you gain a skill. However, as your fishing level increases, you need to catch more fish for a skill-up. At your level, you should consider Steamwheedle in Tanaris. The stonescale eels and clams (for pearls) can provide a little income while you are gaining skill. At 217, you will probably get a skill-up every 4~6 catches. (I don't remember the exact number) You will likely be at 225 within half an hour of steady fishing.