You know how in Gen V, in BW2 you can only get a Gyarados by buying a Magicarp from a guy at Marvellous Bridge who sells it?

Can anyone tell me if the stats of said Magicarp are fixed? Because I just got one with perfect IVs in 3 different stats. I want to know if I just got lucky or was it designed with getting 3 perfect IVs no matter what.

Please answer.