i couldn't find the whole study but here is a synopsis..

"Catch and release has become a major management tool to deal with low productivity streams and the cumulative effect on such waters for competing habitat uses, heavy sport fishing pressure and/or high exploitation by commercial and Indian food fisheries. Among the 336 steelhead angled and released at the Keogh River from 1985 and 1986, mortality was 5.1%. The survival through spawning of angled and release Keogh River steelhead was similar to that of steelhead which were captured at the fish fence 400 m upstream from the ocean. The number of steelhead caught immediately downstream from the fence, tagged, released immediately upstream, and later trapped as emigrating post-spawners represented 27.5% of the available population. This was only 5.4% lower than the recovery rate for fish which were not angled. Comparison of the degree of hooking injury with mortality rates revealed, not unexpectedly, that mortality was highest among fish that sustained severe blood loss when the hook pierced or tore a major blood vessel. However, 47% of the most seriously injured fish recovered, and were released in what appeared to be a healthy condition. These results refute claims that caught and released steelhead were effectively lost from the population."

my notes...
so fish that are caught and released nearly always survive the experience unless there is major blood loss.. nearly half of even fish with major blood loss survive.. so.. most of the fish that are caught and released that die die from excessive blood loss.. Of the hundreds of steelhead that I have seen caught and released there was exactly 1 fish that had any blood loss at all let alone major blood loss.. if nearly half the fish with major injuries survive how many with no injury survive??

Here is the truth guys nearly every steelhed caught and released in catch and release fisheries does not suffer blood loss.. so very few of them die.. Of the very few that are injured half survive... that leaves very few fish that die from catch and release fisheries.
Wild steelhead almost never die as the result of being caught and released any way you slice it...

arguments against catch and release fisheries are totally bogus in my opinion and in most cases based less on science of knowledge than on bitterness and anger caused by feeling excluded from a fishery because the person feels he must kill what he catches..
Catch and release allows sport fishing to continue at no threat to the fish population even in areas where steelhead runs are depressed.... you may not like it but thats the truth..