The canyons just below Bend Bend park are called the Lower Canyons. Not sure if those are the ones he's referring to, but they are about 7 day minimum float, so, it sounds like that section of the river.
Finding fishing information on that part of the river may be difficult to find. Not that many people have been there. The closest I ever got to them was floating Boquillas when I was in college.
I'd take a rod with me, there should be some bass and other warmwater fish in there.
Good luck, it should be a cool trip.
Rex
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Rex W
FFF Certified Casting Instructor
TFO Pro Staff