I searched Google for the “world’s smallest game fish”, and came across an interesting article on Fishing Fury. The article is about tanago fishing in Japan. Tanago are tiny freshwater fish that are targeted by anglers using super light bamboo rods, human hair as fishing line, and micro hooks. The point is not to catch the largest one, but rather the smallest. The smaller the tanago you catch, the more skilled you are considered. This is surely ultralight fishing taken to the extreme.
Anyway, I don’t want to ruin the article for you. It’s definitely worth a read. Here’s the link:
I’ve never seen that before, it’s very interesting trying to catch the smallest fish!