I would be interested in seeing if Catch and Release produces less casulties in certain areas.
I am thinking if areas with a high proportion of coarse anglers produce better results, working on the logic that they "may" handle fish a bit better. Not proven of course
Also areas that have a high proportion of say rivers where fish tend to be fitter and water cooler/more oxygenated. The same goes for highland lochs with cooler water and so on.
Lumping a southern, manmade, highly stocked lake in with a vast, wild highland loch gives a poor indication of the true figures, I think.