Says someone typing on a computer, using the internet, mobile phone etc when they don't know how any of them work.  Hilarious.  (By the way, I am a now-retired scientist, still waiting for my first payment from the UN...)

The points raised re handling are absolutely on the money as poor-handling techniques are undoubtedly a major factor in survival rates - damaged gills, etc.  I'm not a fan of venting purely because the thought of some clown with a sharp needle taking a few wild stabs at the gut of a fish doesn't seem like it'll end well if you're on the receiving end. Maybe if you know what you're doing then it's an option but given the number of iki'd fish I've seen still flopping around in a chilly bin, the finesse and skill level possibly is beyond some people. 

Getting a snapper back to a depth where it can re-pressurise with a weight and a simple rig is easy and effective - we have one on the NZ Fishing News project boat which is essentially a 'puka weight on a handline and it works fine. The main reason I'll release a larger fish (when the depth and condition align for snapper in particular) is to look after the gene pool. 

Big healthy fish pass on big healthy fish genes and in my view that's a good option as we all want of more of those fish in our inshore fisheries don't we?

I've also released plenty of snapper in deep water that have shown no signs of being 'blown' that have headed straight on down.

As for the big fish genes, I'm a fence sitter there simply because if there is such a thing (I don't have to agree with everything Grunta says :) ) then clearly the big fish have it. Of course all big fish were once little fish too but we can't tell if that 27 to 70cm  snapper has those genes. 

Here's another one, most of these debates revolve around snapper. I've never seen a 'blown' kahawai or kingfish, Jack mackerel, tuna, marlin etc. It's predominately the demersal fish that have these problems but not always. Snapper & gurnard are especially prone but other demurrals such as spiny dogfish, of which I've caught at least two billion (you're exaggerating again Smudge) don't get blown. I've also seen crayfish caught in 50m still looking healthy as

Random musings but everyone seems to only think this is a snapper problem. Hapuku seem to be affected pretty badly too but then again I've yet to catch a snapper in 300m

Does anyone release hapuka? 

My own musing. What I've seen time and again is that bigger snapper suffer barotrauma to a much greater degree than smaller fish. Apart from being annoying, I've never heard an explanation or anyone else talk about it. You have to factor in length of fight, i.e. bigger fish will have a longer flight and may be exhausted from the fight itself and therefore more likely to die, but you would have thought a longer fight would mean a slower ascent and less barotrauma?

That is sensible Krow.  The killer here is volume change.  Those of you who dive will know that every 10m of water puts another atmospheres pressure on the body and any gas spaces.  Net result is that the largest volume change is close to the surface.  Going from 10m to the surface the volume of any gas spaces will double (Going from 20m to 10m depth the volume increases by two thirds).

10m to surface pressure change is 100%

100m to 90m is still a 10m change but the change in pressure is 10%

Puka fishing I've noticed they put up the last hurrah desperate struggle at around the 100m mark and I'm guessing that's when they start to get blown. 

Couple of technical corrections from the physics police here guys.

Yeah -I got it wrong ... (which is a little embarrassing)