Ok now I'm on the subject.
Circle hooks were a ploy devised towards live bait use. Why are not circle hooks not in flavor for artificial lures ? Has never a fish been gut hooked or mortality wounded from an artificial lure / fly before ?
So if the studies conclude live bait has a higher risk of the fish impaling the bait and hook into its stomach, what does the circle hook achieve over a standard j hook. ?
In my findings, there is zero difference trying to retrieve a circle hook from a gullet than a j hook. In fact, its worse when the curve point of a circle penetrates.

The stupid justification theory to me is that bait gets engorged, artificial don't which is completely hogwash from anyone that actually fishes.
The other justification is that the curvature of the hook detours penetrating if swallowed. Do they realize how many people now let their fish swallow the hook using a circle and live bait as opposed to setting on a bite with a j hook. This stuff is so unrealistic it's sad

My thing is stripes on the fly, and since that's the case, I have run across quite a few people that are of the same mind as me. If they, or I, thought circle hooks were an advantage in reducing mortality or increased hooking ratio, we'd  be using them religiously. Instead, having tried them, they were found to increase mortality in bass under thirty inches. I learned how to successfully remove a  deeply taken fly out through the gills from ichthyologists and marine biologists and the stats that back up the survival rate from doing it. With the circle hooks, you can't  disengage the barb and the only option is to cut the hook with strong dikes.  In some cases in bait fishing the hook will pull forward and engage the corner of the jaw, but that doesn't happen with regularity.  Not everyone treats a striper to be released as if it were on an operating table. Barbless is a thousand times better. Just pinch over the back of the barb and leave a  bump to keep the hook in place. With all the tech we have today, a better hook could be invented. 

Think its the old story that circle hooks 'always' catch in the corner of the mouth.
Great advertising that has stuck in the mind as opposed to reality.

I've caught trout on flies that have swallowed the hooks off the surface so it's really no matter the species, it happens.

With circle hooks, the theroy is to let the fish take the bait then slow pull it from their internals so it will slide into the corner of the mouth. Hogwash....
The only way circles work as intended is if you use a 2-3 times gap size.
If I'm using a size 4/0 J or octopus hook then I'm using in comparison a 8/0 circle to achieve the same results.
There is not one single person I know that will not put a size 6 or 8 J hook on their line instead of a 2/0 or 4/0 circle hook to achieve the same hook ratios