This one looks like Someone Hole ?
You can have the Grande Cascapedia any time .The public waters on the Bonnie are as good as most "reserved " areas on other rivers . Did you try the tailout in Petite Black ??
BTW I fish Grand Black from two different approaches.Using dries with either an 11"or 14 ' Spey or at the tailout with a #4 7ft rod .Sometimes use a Sneaky or Leach in the middle of the pool .
BTW #2 I've got some good underwater shots of Salmon in Grand Black.I should figure out how to post them here !
BTW#3 There are sectors on this river that are "not accessible to the wading fisherman", with a Spey rod you'll be fine ! For example, Leaving Camp Melanson on the Petite @ 4:30 A.M.,40 minute walk in ,36 minutes on the river ,2 fish @ 12lbs ,on the roadto Montreal by 7;45 !!