A study just published reaffirms why, anglers ought to be using circle hooks - unless they intend/expect to keep every fish caught.
The North American Journal of Fisheries Management published online in late July a study titled, "Catch-and-Release Mortality in Subadult and Adult Red Drum Captured with Popular Fishing Hook Types." The study looked at redfish release mortality for circle versus J hooks, noting an enormous surge in the numbers of this most-popular inshore game fish being released.
The result leaves absolutely no doubt of far less mortality with circle hooks (particularly with nonoffset circle hooks - that is, with the hook point lining up in the same plane as the rest of the hook; offset circles still showed less mortality than J hooks but greater mortality that nonoffset circles). The proportion of deep-hooked fish with circle hooks was virtually nil versus J-hooks with nearly one out of three reds deep hooked on Js. Circle hooks proved "significantly more successful" at hooking fish, also, so what's not to like?
Bottom line is clear enough: If you haven't made the switch (to circles) when fishing bait, you should, except in specific fisheries where for whatever reason J hooks are essential.