ATHENS, Texas-Most anglers probably know that many fish caught from deep water can suffer from an over-inflated swim bladder, a condition called hyperbuoyancy. The air bladder inside the fish that inflates and deflates to give the fish neutral buoyancy can expand suddenly when a fish is brought to the surface after being caught. This puts pressure on other internal organs and may even lead to the stomach protruding from the fish's body.

The fish may also be unable to swim upright and submerge. The fish will float at the surface for several hours until the swim bladder depressurizes. This condition by itself may not be lethal, but the fish expends a lot of energy trying to submerge, and it may be struck by a boat or killed by a predator.

Not all floating fish die, but enough do to be a concern.

What anglers and even fisheries biologists don't know is the best way to treat hyperbuoyancy in order to increase survival of fish after they are released.

Texas Parks and Wildlife Department Inland Fisheries biologists intend to find out.

"It's important to understand that if you catch a fish from 30, 40, 50 feet deep and immediately release it, it usually goes right back down with no problem," says Randy Myers, Inland Fisheries district biologist from San Antonio. "Even after it goes through the struggle of being caught, the fish may have enough energy to swim back down to a depth where neutral buoyancy is regained. But if that same fish is kept in a livewell for several hours with an over-inflated bladder, it becomes exhausted from struggling to stay upright and floats on the surface."

Budweiser ShareLunker program manager David Campbell has probably dealt with more big bass suffering from hyperbuoyancy than anyone else, and he feels that fish can develop hyperbuoyancy for several reasons. "I strongly believe that exhaustion happens when the fish is trying to adjust to its environment, whether that is caused by being pulled from deep water, the stress of being caught, lack of oxygenated water or being in a crowded livewell," he says. "When a fish has room to swim but starts swimming nose down, has to fight to stay down or swims right-side up but never stays more than a few inches below the surface, it has preliminary hyperbuoyancy symptoms and needs relief-and the sooner the better for survival."

Three techniques have been developed to deal with hyperbuoyancy. Two involve puncturing the air bladder to vent gas and reduce the pressure, a procedure commonly called fizzing because when done properly while holding the fish underwater, a stream of bubbles is released.

Fizzing can be done by inserting a hypodermic (hollow) needle into the air bladder through the fish's side or mouth.

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