There is no easy answer to your question "what are the dredging restrictions there?". PNG citizens (nationals) can legally use suction dredges in PNG rivers if mining is carried out in accordance with the Mining Act ( www.mineral.gov.pg/docs/acts/MINING_HANDBOOK.pdf ) ... however for non-citizens to dredge in PNG it is much more complicated (but not impossible).
For a non-citizen (known in PNG as expats) to mine gold in PNG they would, at the very least and as a first step, have to obtain permission of the landowner to dredge. In PNG land is regarded as more valuable than anything else and land ownership is a complicated issue for expats. In PNG, land ownership is the opposite of what we understand land ownership to be in the developed world. In PNG every square inch of land is "owned" by someone, with nearly all rural land known as customary land ... which is "owned" collectively by a tribe. And the rivers are regarded as much a part of the customary land as a hill or any flat land or anywhere else in a defined tribal area that has been determined historically. Also, rivers can often be the boundaries between two tribal areas and this can further complicate "ownership". In PNG rivers are not in "public" ownership as they are North America or Australia.
Its probably worth retelling in this thread a story which is well known among the independent miners of Australia. Back in the 1980s an Australian independent miner went to PNG with a metal detector to detect for gold nuggets and went into the highlands to detect. He did manage to get some good size nuggets until one day when he was challenged by a PNG citizen from the local village who told him he did not have permission to do any mining and he must surrender all the gold he had found. It was the Australian miners bad luck that the PNG citizen who confronted him was the then Minister for Mines who happened to be visiting his home village just at that very moment in time. The Australian miner then spent that night in jail and was shortly after expelled from the country. Somehow the Australian miner did manage to get his detected gold out of PNG and he probably thought a night in jail was worth it. But ... he probably had no chance of ever returning to PNG. If it had happened these days he would probably not get off so lightly.
Hi All, hope that you are getting good gold.At the currant price all of as will be millionaires soon I am commencing a pro gold dredging operations on 1Nov 2010 with 20 Pro -SD 8000 -8" .We will need dredgers /supervisors for this project If any interest ,please let me know! email email@example.com Mob: 67571735554