Interesting:
http://www.tpwd.state.tx.us/fishboat/fish/didyouknow/inland/livewells.phtml
Anglers should be aware that during summer the vast majority of tournament fish mortality occurs one to three days after release back into the reservoir. Recent TPWD studies involving major tournaments at Amistad showed low initial mortality year-round, but high delayed mortality for summer-time events.
Initial mortality represents the percentage of tournament fish weighed in dead and ranged from 1.7 to 8.7 percent among five tournaments held from January to September. For each of these same tournaments a large sample of tournament fish was placed into large holding pens to determine delayed mortality, which is the percentage of fish dying within three days after release.
Delayed mortality was low (less than 5 percent) for tournament events held when the reservoir water temperature was less than 65 degrees. However, delayed mortality ranged from 18.2 to 43.1 percent for tournament events held when the water temperature exceeded 79 degrees. Totaling initial and delayed mortality for one of the studied tournaments revealed that 50.1 percent of all weighed-in fish died at that particular tournament. Anglers should be mindful that many of the fish released alive back into the reservoir during summer experience mortality a short time later. Although use of proper livewell management and fish-care procedures will somewhat increase the likelihood of long-term survival of tournament-caught and released fish, oxygen injection guarantees against low oxygen causing mortality.