There's a watershed in the NW part of the state that I fish occasionally which has a great population of bowfin, and too many times I see them dead along the banks and talked about badly. I'm 99% sure these people who are killing/don't like the bowfin know that they aren't snakeheads, but they think they are just as harmful.
Since this location is special(because of the bowfin pop.) I'm guessing this poster will go there, and I surely hope these people start taking better care of the fish though I highly doubt it, as I said these people know they're bowfin but they still think they cause a lot of harm to the fishery.
On a side note, fish identification by fisherman is really lacking I noticed. I've seen people mix green sunfish with rock bass and vice versa too many times and if they can't correctly identify those species then there's no way they can tell the difference between bowfin and snakeheads, and they'll start second guessing themselves since the sign is present(which is unintentionally saying there could be snakeheads in the watershed), killing maybe the darker colored bowfin thinking they're snakeheads. Hopefully the sign helps, but I guess only time will tell.
Sorry to rant a little. Though I may not have sounded like it, I think these posters are a GOOD thing and hopefully it stops some unnecessary bowfin killing.