"Common hook" means any hook or multiple hooks having a common shank. All
hooks attached to a manufactured artificial lure shall be considered a common hook.
That is from the CDOW 2013 fishing regs book found here
I have personally interpreted that sign to mean no treble hooks. I have used tandem or even triple nymph rigs all over the Ark depending on where I fish. I also use several articulated streamers, some times tandem, but my front hook on all mine is cut off only leaving the stinger.