As of this moment, if it is Essential Salmon Habitat (ESH), Bull Trout, or Threatened Cutthroat areas, no motorized equipment allowed in the waters or within 100 yards on either side if it affects water quality.  That determination is up to the officer on the ground talking to you.  The exception is waters that have no fish passage, ie. a dam on ESH with no fish ladder or wheel, or some natural impassable feature (like a waterfall they can't get over).  Motorized includes electric or battery operated equipment, as well as gas engines.

That being said there is a bill in the legislature that will add those now open waters to the moratorium.  SB 1530, you can track it on line, just search for Oregon Legislature bill tracker and plug in SB 1530.  As of Friday (19th) it was in committee and had not yet hit the floor.

There will eventually be a small public panning only area in the Prairie City area when the new BLM management plan is implemented, but that is probably 3-5 years out right now.

If by hand dredge you mean a sucker tube, you are good to go with those, along with hand tools, pans and non-motorized sluices.  Gravity dredges are also included in the moratorium.   Also be aware of 303 listed waters and motorized equipment.  303 listings can be for a varity of reasons from iron, mercury, arsenic levels to sediment issues to temperature.

Your electric recircs are good to go, but if you plan to pump water then you might fall under the 600 permit.  If you are talking just a few gallons of water in a bin, you should be OK.

As far as metal detecting, as long as you are prospecting you are good, if you are relic hunting then the 50 year old rule falls into place on public land.

Thanks for the references