I do, I spent about an hour doing it just for fun. To scoop goldfish, you talk to the NPC in charge of the scooping and ask them for a goldfish bowl, then purchase a few "Super Scoops" from them. Now you equip them as the NPC tells you to and go to the nearby body of water, proceed to use them as you would use fishing gear. The goldfish you get can be traded into the NPC for points that you can use for fireworks, more scoops, or traded for the contents of a "mystery box"... which I assume is a nifty random prize. When I got the mystery box it contained 12 "Spirit Masques" but I bet that you can get nicer things from it as well.
Overall it's not a major thing, no real affect on gameplay, unless you eat the fish, and I'm not sure what their stats are but I saw someone eat one so I know that you can.