In the video: Hurricane Irene flooding has further damaged the weir and possibly exposed a wooden stake.
Hurricane Irene damage (the Water Company also released water before the storm which may have also caused damage) further deteriorated the weir. Note the drill holes and, at the downriver end, toward the end of the video, a possible wooden stake between stones...
"Weirs were described in 1634 by the Jesuits as ingeniously made, long and broad and capable of holding five or six hundred eels and having collected stones extending out on either side like a chain or little wall to direct to eels (Thwaites 1896-1901:6:309)."
Otonabee Pimizi, American eel (Anguilla rostrata) on the Journey to “The Land Between”
by William Arthur Allen
“Land Between” Research Forum Peterborough, Ontario June 7, 2007