In the river I grew up on, this was called "clam dredging". One county (across the river) allowed it, our county did not. In those days, the bottom of the estuary was mostly sandy, so turbidity was not generally a problem. Now, those clams are extinct, not because of dredging, but because of the ACoE eliminating aquatic vegetation (over 40 years ago) and two incursions by schools of cow-nosed ray which wiped out the clams, but which would not have likely have happened if the vegetation had been intact. (Thanks to the ACoE, commercial fishieries in the area pretty much collapsed within 10 years).