I'm trying to fish these falls for hybrids and looking for advice. The spin fishermen aren't having any trouble hooking up. What would you suggest? Time of day, floating or sinking line, cast into the fast water or otherwise? Any help is appreciated!
I would pay attention to where the spin guys are hooking up & fish there.
There's no question what the best times of day are... The 30-45 minutes that are first light & sunset.
I'd say the best is from pre-dawn twilight through the first 45 minutes of light. The water has had all night to cool, as well as calm down from all the people fishing/wading/canoeing whatever it is they're doing there. My first cast I would want to be the only one there & my fly the first thing the fish have seen for the day aside from the real deal.
I personally use floating line for everything in Ohio. I control my depth with my leader material. In a situation like yours, the fish will not be deep, they'll be chasing bait in the upper portion of the water column. (+/-3' probably) A sparse clouser & 1x tippet will get you down plenty far.
I almost always cast into the uppermost part of the riffle & left my fly drift down into the tailout.
If the fly isn't taken right off the get go, I'd expect a take as it slowly drifted through the area right where those guys are standing, i.e. the calm pockets of deeper water immediately beneath the flowing, bubbling water.
2 reasons the hybrids (and bait) are in that water. 1.) The obvious one, they can't go any farther upstream...and 2.) the important one, temperature. The hotter it gets, the less oxygen is in standing water. The water falling over the dam is being aerated & thus attracts fish of all kinds, especially bait.
Another thing you can do which others probably don't...depending on the depth, as long as it's 2' or deeper...I'd fish right up against the bottom of the dam there. That's where the bait will be getting corralled, at the absolute farthest point the fish can go upstream.
It looks worse than what it is. The deepest section is about 4 feet deep. The bottom is large rocks so you have to go slow but there were 6 of us out there and no one fell down. They all had much better luck than I did though with chicken livers.
Just looking at the picture, not knowing the channel, holes, etc. I would move farther downstream & fish the first actual deep hole you come to... also behind those bridge pilings if they create current break.
Another strategy, fish it when nobody else is... when it's up high or on it's way back down. Safety is number 1 concern of course but if you can access current breaks when the water is up you'll find schooled fish, hopefully.