My husband began fishing with the kids last year after a good afternoon of begging by the children. I do not know what they thought was going to happen, but they just HAD to go fishing.
My husband used to fish with his mother when he was young, but didn't particularly enjoy it. It was a classic case of miscommunication. Aaron's father died when he and his brother were young. Aaron's mother wanted to make sure they didn't miss out on any of the male-oriented type activities, so she took them camping and fishing regularly. Turns out that they only did it because they thought she enjoyed it and she only did it because she thought they enjoyed it!
What do you know? When Aaron took the girls out last year, he decided that he actually did like it. And so do the girls. You won't catch them filleting a fish, but they're out there watching the whole gruesome procedure--so they could someday if they chose. They even enjoy it when they don't have anything to bring home. Last time he went out, he actually taught the eight year-old how to cast.
GeekDad has a post pointing to a fishing how-to for kids so you too can introduce your children to the joy of waiting and satisfaction in having actually accomplished something so profound as to actually provide their body with sustenance. It's not as important as differential equations in my opinion, but only one of those can be done by an eight year-old or five year-old.