The fish Pokemon Basculin
This a new fish Pokemon in the 5th gen Pokemon games and has two forms though you cannot change it, Whichever form you find it in is how it'll stay. Good news is you can get both of it's forms in each game. Its Red stripe form is more common in Pokemon Black while it's Blue stripe form is more common in Pokemon White. While your fishing or surfing spots of water you'll sometimes see a round dark blue spot. A lot of the time when you surf over to the spot or fish in them you might run into the rarer form of Basculin.
Added by: Ninetailed Fox Jan 29th 2011, ID#15181