With all due respect to the large number of fishermen (especially fly-fishermen) who respect the environment and clean up after their activities, a significant percentage of their colleagues seem to be oblivious of the mess that they create and the environmental damage that it may cause.
Discarded beer cans, lunch debris, cut lines and an assortment of floats, weights and empty containers often litter their abandoned fishing site. Just this morning, I came across such a scene of desecration at South Platte Park, an otherwise pristine nature preserve.
Unlike hunters, who generally seem to connect with the ecosystem in which they seek their quarry, many fishermen are present solely for the recreation, bringing along their folding chairs, music and sustenance. I doubt that many of them can identify the birds and mammals that share the lake or river and might be endangered by the garbage that they leave behind. In my personal opinion, fishing should be restricted (if not eliminated) within sensitive natural areas; pelicans, cormorants, diving ducks, mink and other native wildlife will keep the fish population under control.