Although I'm not writing this as a "recommendation", I will say this:
I've been busted nearly a dozen times for fishing without a license. Bellingham, Washington...Laramie, Wyoming...Littleton, Colorado...Lawrence, Kansas....Ketchikan, Alaska, just to name just a few of the places I've been busted fishing without a license.
However, I have never received a fine, and this is because I politely and respectfully explain my position, and I fully apologize:
"Oh shit, I'm sorry man...I'm just a homeless traveler passing through town, inbetween seasonal jobs, and I just wanted to see if I could catch a small fish to cook for dinner tonight. I apologize and I'll put my pole away if I'm causing a problem, I just can't afford a license. I'm really sorry, and you'll never see me again sir"
For me, that has worked 100% of the time. Half the time they even let me continue fishing, and will stick around to hear stories of my travels or get some hobo-fishing-advice from me.
Honesty and respect will get you a long way with wildlife officers.
Once again, I'm not saying this is a recommended way to fish, nor am I saying this will work 100% for you as it has for me.
Your best bet, always, is to scope out the area first. Try to hide in some bushes by the bank, or even better, walk downstream/upstream a few hundred yards from the popular fishing spots to avoid anyone seeing you period.
Just my two cents based on my experience.