The problem is that dissolved oxygen levels drop during the summer when water temperatures soar, and that stresses fish.
When caught, largemouth bass become more stressed and can suffer higher mortality rates.
To minimize stress on the fish, catch-and-release anglers should land fish quickly and handle them 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, which is the fish's main defense against infection and disease.
"Before you touch a fish, always wet your hands," NCWRC's Brian McRae said. "Return the fish quickly to the water if you do not plan to keep it or place it in the livewell."
Also, the type of net used can be critical, McRae said.
"When using a landing net, a knotless nylon or rubber coated net is preferred over a knotted nylon net," he explained.
Tournament anglers 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.
McRae also recommends that tournament participants fill their weigh-in bags with livewell water, not reservoir or river water, before putting in their catch.
Also, only put five fish in a bag, fewer if the fish exceed 4 pounds each. McRae also said anglers should limit the amount of time fish are held in bags.
"Keeping largemouth bass in weigh-in bags for longer than two minutes will significantly increase post-release mortality," McRae said.
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 re-circulating 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."