Why can you fish with lead but not hunt with it?

You are referring to rules that require the use of non-lead shot for waterfowl hunting.  Lead shot was prohibited as per an agreement with the U.S. Fish and Wildlife Service who regulate the harvest of migratory birds throughout the U.S..  Studies showed that large amounts of lead shot were being deposited in wetlands from waterfowl hunting activities and much of that lead was being ingested by diving ducks.  Several cases of lead poisoning of waterfowl were documented in wintering waterfowl areas where hunting occurred.  Idaho, like other states now only allow waterfowl hunting with the use of other shot materials including more expensive steel and bismith shot. In Idaho, we have not documented any cases of waterfowl or other wildlife or humans being poisoned by lead sinkers that are lost from fishing activities.  We are, however, aware that this is an issue that has been brought-up in other parts of the country.  Until a problem has been documented in Idaho, we are not incline to require more expensive nonlead sinkers while fishing.