Ok... I'll play devil's advocate here, not for the fool in the pic, but for the actual question of the forum.
1. I can't prove it, but I think it is a safe assumption that catch and release is more common now than 30 years ago.
1a. If we are honest with ourselves, Missourians have had a... not so good relationship with the "feds" and their rules going back to the civil war. I don't think following the rules is ever been a strong point.
2. In 1983 the population in Missouri was around 5 million; in 2013 it is 6 million. That is a lot more people, and there is the same or even less amount of water.
3. I wasn't here, but this forum as told me:
3a. There was a much smaller aluminum hatch 30 years ago.
3b. The banks, bluffs, and river bars were firmer, and thus, there was better habitat. Great habitat equals great fish.
4. Two words... urban sprawl.
5. Jet boats have opened up water to those who wouldn't want to work for it. Equals: more people fishing.
My point, this kid and those like him are probably not the primary reason the decline in fishing.