On a different note, I'm trying to recall when I don't find mercury. It always seems to be present where streams were worked hard by the Oldtimer's as many of them used it to trap the fine gold, and they were not careful with it, as it got in the streams they were working on a regular basis. Then, there's streams that weren't worked that still have mercury in them--elemental mercury--naturally occurring mercury. I have got gold from gold-bearing streams and never seen a sign of mercury; so, yes, and no.
As well, I've found it while dredging, but then again I haven't (depending on the stream); so, once again, yes and no.
The only time I use gloves when doing regular panning is when the water is stinkin' cold--the thought of mercury has never entered in to it. Now, if I'm using mercury to concentrate and amalgamate--absolutely.
All the best,
Lanny