I have found (through diving) that there are many small fish within the 20 foot range of the shore (20 feet deep that is). However, I notice that many of them seem to be young versions of much larger fish I see out deeper. Especially things like perch are cute and tiny close to shore and huge out deep.
If it is legal to ctach your own pets where you are then I say great, but do make sure that you know the species of fish you catch or you will have lots of trouble.
Another issue might be trying to keep the water cold enough. In the summer these fish are in water that is 40-50F and this goes up to 60 in the fall around here. That is pretty darn cold and you will have a lot of trouble trying to keep things at that temp.