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Aug 2011 cover image State parks

Splash, Splash! Fizz, Fizz!

Scientists test cures for overinflated bass.

By Dyanne Fry Cortez

When a fish is caught from deep water and hauled up to the surface, the sudden change in pressure may cause its air bladder to overinflate. This leads to a condition biologists call “barotrauma.” Eyes bulge, the belly swells, and the fish may float helplessly, too buoyant to submerge.

“Barotrauma to fish is like ‘the bends’ are to scuba divers,” explains Randy Myers, a fisheries biologist at the Texas Parks and Wildlife Department.

A technique known as “fizzing” — puncturing the air bladder with a needle to vent excess air — can relieve symptoms of barotrauma. But what’s the long-term effect? Does it improve the odds that a fish will survive, or can it do more harm than good? Is it something an angler should try? If so, what’s the safest, most effective method?

Myers led a recent study that sheds some light on those questions, specifically in regard to fishing tournaments and largemouth bass.

The study site was Amistad Reservoir. It’s 200 feet deep in places, a prime spot for barotrauma. Researchers attended five bass tournaments, examining more than 3,500 fish. Forty-five percent showed signs of overinflated air bladders. Biologists kept a sample group, half with symptoms and half without, and watched them for several days to see how they fared. Survival rates were good for both groups, especially when the water was cool (60 degrees or below). This suggests that many bass caught from deep water will recover on their own. However, “fish that have barotrauma, left untreated, are less likely to survive than fish that do not,” reports Myers.

For the next step, researchers induced barotrauma in a test group of 466 bass and compared three ways of treating the condition in the fish:

  • Side fizzing, where a hypodermic needle is inserted in the swim bladder just behind the pectoral fin.
  • Mouth fizzing, where the needle is inserted at the back of the mouth.
  • Deep release or “caging.” Instead of being released at the surface, fish are placed in a weighted cage with an open bottom. The cage is lowered to the desired depth and pulled up, leaving the fish behind.

After analyzing the results, Myers is willing to make a few recommendations.

Side fizzing doesn’t appear to hurt the bass, and it isn’t difficult to do. If a tournament-caught fish shows signs of barotrauma, “we recommend that the angler go ahead and side-fizz the fish, within the first hour if possible,” Myers says.

Deep release also works, but that would have to be done at the weigh-in point after scores are tallied.

Fish that were mouth-fizzed fared worse than those that weren’t treated at all. Some bled excessively, and a significant number died. Researchers can’t say for sure why this happened, but Myers can make an educated guess. “When you use mouth fizzing, you’re piercing the business end of the air bladder. That’s where all the nerves and blood vessels are,” he says. “We don’t recommend that treatment.”

One more thing: the average catch-and-release angler needn’t worry about fizzing bass. A fish that’s released quickly will have enough energy to fight the buoyancy and go back under. If it swims down to the approximate depth where it was caught, the air bladder will deflate and symptoms will go away.

A bass that’s held in a livewell, awaiting weigh-in at a tournament, struggles to stay submerged. “After about 10 minutes,” Myers says, “it gets exhausted and rolls upside down.”

Nobody wants to see schools of bass floating belly up at the release site of a fishing tournament. It gives tournaments a bad name. And while they’re struggling at the surface, bass run a greater-than-usual risk of being run over by boats or eaten by predators. If a needle in the air bladder can help them get home sooner, it’s better all around.


Side Fizzing a Bass

1. Grasp fish by the lower jaw or around the head region, and position fish so its side is facing up and at the water surface.

2. Position the pectoral fin flat against the body in a natural relaxed position pointing toward the tail.

3. Identify needle insertion location, which is two to three scales behind the tip of the pectoral fin.

 4. Orient the beveled side of the 16-gauge, 1½-inch needle facing up. At about a 10- to 20-degree angle, slide needle tip under trailing edge of a scale toward the fish’s head. 

5. Submerge fish and needle, raise the needle to a 60- to 90-degree angle, and insert needle until air bubbles exit the needle base.

6. Vent small fish (less than 3 pounds) for three to five seconds and larger fish for five to eight seconds.

7. Remove the needle and observe the fish. If the fish cannot resubmerge, vent additional gas from the fish’s air bladder as described above.

8. If bubbles don’t exit the needle, check for blockage by blowing through the needle. If blockage persists, clear debris from needle using a syringe.



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