As a fellow angler myself all i can say is , turn the other way. You have to change how you see things as an angler, for example, when i first started fishing the 3rd fish i cought died on me, as i love and keep fish this was initialy a sad experiance but, TIF ( this is fishing) there will unfortantely be times when a fish is too tired from a fight or swollows a hook and will inevidably die, its sad but its part of the spot and one has to come to terms with it, same goes for people breaking the law, using nets or catching and killing big ole fish, what can you do? nothing really.
All you can do is lead by example and practice catch and release. I too fish at a lake that has no one come to check permits or to generaly walk around and check people are doing the right thing, it buggs me that people throw their trash evryware and that there are fire pits even though the sighns state that no camping is allowd, no fires etc. you just have to move on and get over it or it will ruin the sport for you.
Cheers-
Dazz