at jubilife or enterna city
in the somewhat tall grass. or when you are fishing with a fishing pole. or when you run into a Pokemon when surfing on water.
fishing or surfing
You can find Pokemon in grass, caves, fishing or surfing.
magikarp
you get it in the house on silence bridge
By surfing or using a fishing rod
yes you do need a fishing pole to catch mitotic in Pokemon black but you cant catch that Pokemon you have to catch the first evolvation and then you train it until in evolve into a mitotic
out side of hearthome ther is a fisherman standing on the dock were all thoose joggers trying to loose weghit and the kid dressed up as a pikachu.:]
there will be a man fishing in sunnyshore city
go fishing in the great marsh
go to the lake of rage
Heck if I know!! Haha