Don't all the fishing gurus just say "hey buddy, you like fishing?" And you're all "Totally rad sir" and he's all "awesome, take my prized possession". Anyway yeah, maybe Gearuvagen's right. Just to confirm it, he's in the house above the Pokecenter. In fact, I'd bet my money on it that Gearuvagen's right. The trader is in the left-most house by the lighthouse, pretty much exactly north of the Pokemart.