Fish and worms...I don't get it

I'm not really sure where this is coming from, but for some reason today I was thinking about fish...just kind of out of the blue, for no particular reason. I like to fish, so maybe that's why I was thinking about it. Getting to the point though, I just don't understand why, when you're fishing, you can catch a little fish and throw it back into the water, and sometimes they just keep coming back and eating the worm again and again to get themselves caught. I just don't understand it. I realize that the fish have got to eat, that's just a fact of life, and I understand that. But I just kind of think they should be smart enough to at least be a little bit scared of the worm and not go swimming up to the very first one they see after getting caught. God made animals with instincts to follow, which I suppose is why the fish does that. But didn't God also make them smart enough to make choices? I suppose that's a choice that the fish has to make: decide to take the chance of getting caught or eating. Either way they could die. It all comes down to choices. The same thing could be said about people. Why do we make the choices that we do? Sometimes it seems like we have so many choices to make and we end up making the wrong ones. I hate not knowing whether I should just go with my gut feeling or if it needs more thought. Sometimes I wonder why we have the power of choice... it complicates things, but then again we wouldn't be happy without it. That's what makes us human. It confuses me, but some things just aren't supposed to make sense to us.