Hi dave. The Lower Niagara is the mecca of migrations. it hosts salmon, steelhead, browns, and lakers. All are Lake Ontario fish. It also has incredible resident populations of fish like muskie, sturgeon, and walleye. The whirlpool is particularly special as it is the end of the line (as far as an upstream migration goes). But in safer times of year you can walk down the glen and fish along the river. Access is challenging you must be very able bodied.
All these species successfully spawn each year, which is evident in the various year classes and large populations of fish that keep returning.. it is their natal "stream". As guys said above, you have to gear up to fish it properly.. heavier floats, larger weights.. you should also experiment with changing you float depths. start in the 5ft range close to shore along seams, then lengthen your lead and cast farther out into a deeper seam. (I use a slip float with a bobber stopper to get 10ft+ deep when drifting it).
hope that helps.
JKW