you can find the old rod on route 32 or you can find the good rod in olivine 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.
In the water while fishing In the water while fishing
at jubilife or enterna city
magikarp
you get it in the house on silence bridge
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
Heck if I know!! Haha
go to the lake of rage
Fishing pole? You use a Super Rod to catch it. There is no fishing poles Pokemon,only Old Rods,Good rods, and of course Super Rods.
Once you have a fishing pole in Pokemon go to a large body of water and cast the rod, after a little bit you will get a bite and a Pokemon battle will begin.
on route 32 in the Pokemon centre talk to the fisherman
press spacebar or z