Proper Catch and Release Techniques for Largemouth Bass
The following list of tips from the North Carolina Wildlife Resources Commission should help reduce mortality when releasing largemouth bass back into the wild.  
To minimize stress on the fish, a catch-and-release angler should land the fish  quickly and handle it as little as possible, including removing the hook from  the fish’s mouth while it is still in the water, if practical.  Limited handling  helps reduce the loss of slime coat, the fish’s main defense against infection  and disease.
Anglers should always wet their hands before touching fish and return the fish quickly to the water or immediately place it  in the livewell. When using a landing net, a knotless nylon or rubber coated net  is preferred over a knotted nylon net. 
Anglers participating in fishing tournaments can minimize fish mortality by  maintaining healthy oxygen and water quality in their livewells.
 A few ways to  do this are:
Knowing the capacity of the livewell and not exceeding a ratio of more than 1  pound of bass per gallon of water;
 Running a recirculating pump continuously if more than 5 pounds of bass are  in the livewell;
 Using aerators or oxygen-injection systems to keep the water’s oxygen level  above 5 ppm; and
 Keeping livewell water about 5 degrees below the reservoir temperature by  adding block ice.
N.C. Wildlife Resources Commission recommends that tournament participants fill their weigh-in bags with  livewell water, not reservoir or river water, before putting in their catch.  They should put only five fish in a bag, fewer if the fish exceed 4 pounds each,  and finally they should limit the amount of time that fish are held in bags. 
"Keeping largemouth bass in weigh-in bags for longer than 2 minutes will  significantly increase post-release mortality," Brian McRae, the Piedmont Region fisheries supervisor for the N.C. Wildlife Resources Commission.
Fishing tournament organizers can do their part to help keep fish alive by  providing holding tanks during the weigh-in with water 5 degrees below the  reservoir or river temperature and with oxygen levels above 5 ppm. 
"Fishing tournament organizers and participants should adopt best handling  practices at all events," McRae said. "Using staggered times to weigh-in,  release boats, and recovery stations with oxygen and recirculating water are all  important considerations when planning a tournament."
Other options for tournament directors who enjoy summer fishing tournaments yet  want to minimize mortality associated with higher water temperatures are  reducing the number of competitive fishing hours or holding "paper tournaments"  without weigh-ins. 
More information on keeping bass alive, including the B.A.S.S.-produced  publication, “Keeping Bass Alive: A Guidebook for Tournament Bass Anglers and  Organizers,” is available on the Commission’s website, www.ncwildlife.org/fishing.
source: N.C. Wildlife Resources Commission