I love beetle hunting on the island at night (restful music), plus if I saw a fin in the water I'd try to catch it. This is how I made the majority of my bells (only did turnips so I could get the gold badge).
I'm not good at beetle hunting. I often scare them away, or they just almost NEVER spawn. Turnip selling is easy if you can find someone with a good price. And plus, if you find a good price and have another person TT to Sunday, both you and him can make bells all day! Trust me, I did that once and I got pretty rich.
I have no idea of what "illegal fish farming" is, but I guess she means just... fishing valuable fish and sharks.
But, to the other side, I absolutely love beetle hunting, and mastered the art of it a long time ago. In fact, 99% of the bells I've got still today were fruits of beetle hunting and some secret methods. (not so secret anymore, I bet.)
I'm an island rat, so when I'm not touring or competitive touring, I'm beetle/shark hunting. I've got so competitive because of island tours, now I feel like a snooty showoff taking pictures of my wins against island people, lmao.