Box 25. 746 Wishiwashi - Solo Form

Ok this is an awesome Idea, a tiny Little Fish that calls its Friends to imitate a Bigger Fish. But Im curious how it works. Shouldnt you need to catch the whole school to use it in Battles elsewhere? I Mean high up in the League, how will the other Fish come up to help the one you caught? Or later on when you travel to a new Region,  will they follow you around?