Its a real bummer, I've gone down there plenty an throwing eggs/plugs/spinners at the mouth is plenty productive. I stopped fishing the area because the snaggers would tangle my gear constantly and look at me like I was the a**hole. I've walked out at dusk many times and seen head lamps walking in. Not enough to snag in the day, seems like a nightime activity as well.
They would need a police station in the park to stop the BS that goes on in there. Until the penalty for snagging fish is big enough, they will continue doing it, and it looked like a family affair in most cases too. Unfortunate that their kids grow up thinking this is how to salmon fish.