Wheim - regarding fish and pain, I have never seen any evidence that fish feel pain. Several reasons for this conclusion.
Fish that have been recently (within minutes) of being badly injured by cormorants go back to behaving and feeding in a perfectly normal way.
I once caught a trout with a fly still in it's mouth, that fly belonged to the angler next to me and had been lost only seconds before, so the fish had obviously not been disturbed in any way by having a hook in it's mouth.
When caught and still on the line, if an angler lets the line go slack, the fish will return to a normal swimming pattern, and will only be spooked when it it restrained again.
Bags - unfortunately you are quite right, some anglers are awful, there is no reason whatsoever for litter or tackle left on the waterside. In my view the increase in carp fishing where sessions can last several days and nights has produced some of the worst anglers - they leave everything behind them, and I do me everything. Tackle can occasionally be lost where it is difficult to recover, but any decent angler will do every thing he/she can to prevent such loss and recover it. On syndicate waters, where there are strict controls, you do not get any litter or discarded tackle.
We get a little litter on our lake due to dog walkers, but we insist that our members clear any litter/mess found, regardless of who/what dropped it, if they don't like doing that, they can go fish elsewhere. (that has never happened yet)
Anglers/fishermen, in my view - anglers fish with rod & line, fishermen fish with nets.