I will first state that I haven't read all of the resonses so this may be redundant; but there are a few things in your original post that I would like to respond to. Before I became disabled I was in the Coast Guard, contact an area Marine Safety Office and they can provide you with a lot of raw data that you can use. You would be amazed as to what is legal to be dumped in the water. In the late 80's it was still legal for a tanker to dump the bilge straight into the ocean, it was perfectly legal to dump 100's of gallons of dirty oil in the ocean!
Additionally in better days I was an avid upland bird hunter, and of course most upland bird shot is 100% lead. I personally think lead is so over rated as a potential environmental hazard. I think of states like ND and SD where pheasant hunting is a multi-million dollar industry, the ground in those states probably have a higher lead count than any other state in the union, with no threat to humans or the wildlife population. As evidenced by the explosion in population of these regal game birds. Sportsmen fund almost 100% of all conservation efforts in this country. The current population of pheasants are a direct result of the CRP and Pheasants Forever. There has been such an explosion of birds that the population is higher now than anyother time, all of that in the presence of filling the field with lead.
If you consider the amount of lead that would have to be present in the water for the fish to somehow become contaminated the ppm would be astronomical. The problem with lead and ducks was that the ducks being bottom feeders would ingest the lead, that and the "tree huggers" were screaming for something to be done, end result is steel shot for waterfowl. The recovery of waterfowl is more due to the CRP and organizations like DU and Delta Waterfowl than non-toxic shot. Studies have since been conducted that show that lead doesn't hurt the reproductity of the bird. There is also a study being conducted now on California Condors, where the main focus is to try to trace the birds decline to lead shot in unrecovered game. Anyone who has hunted knows that the amount of lead in game that is killed is almost non-existent as most passes through, but that is another source of lead info. Bottom line is that lead in the water from fisherman is so miniscule as to be non-existant, and hard to determine whether is directly related to the fisherman, run off, or a natural source.
Personally I believe the only negative environmental impact that people have with regards to fishing, are the slobs who leave their discarded line laying around, the wrappers from their snacks, styrofoam containers worms came in, boxes from crankbaits, etc. Everytime I fish from the bank for cats, or stocked trout I always take a plastic bag and fill it up with trash from these slobs. Makes me sick. I am firmly convinced that recreational fishing has more positive impact on the fisheries than negative. Sportsman today are more educated in general about their potential impact on the fishery. Not to mention sportsmen are better stewards of the environment than any segment of society, after all we have a huge stake in keeping the waters full of fish. To think that sportsmen would damage the environment is about as ridiculous as saying a golfer would intentionally dig up the golf course, we have to much at stake to hurt the thing that we get most enjoyment from.