You have the wrong idea.
Fishing with the gold lure will yield up to 12 lb fish, but only if you fish in gold fishing spots. -.- bait 3 is much better for making big money, especially since the rate for fishes is so high- a grand 1 gralat for 15 lbs. That means you'll geat a gralat for approximately every three fish you catch.
Nevertheless, mining is by far more profitable. I was the richest guy on Graal thanks to mining before the fishing bug made every player 8000 gralat.
So now I just sit around and do nothin'.