Basics of Barotrauma

Doug Leier

By Doug Leier, NDG&F Biologist

For the past couple of years, North Dakota Game and Fish Department biologists have put forth a concerted effort to inform state anglers about a condition called “barotrauma,” which can occur in fish caught from water depths of more than 25 feet.


It’s particularly a concern in North Dakota this time of year in Lake Sakakawea and Devils Lake, when walleye anglers typically find good numbers of fish in 25 to 40 feet of water.


We get a good number of questions on this issue, so I’m including a summary here of common questions posted on the Game and Fish website at


What is barotrauma?

“Barotrauma” is the term used to describe any of the number of injuries, or trauma, a fish may receive from rapid changes in atmospheric (i.e. barometric) pressures. For fish caught by anglers, these rapid pressure changes occur when fish are reeled to the surface from deep water. Most internal injuries are not visible to anglers, but one obvious symptom of barotrauma is the over-inflated swim bladder, which will push the fish’s stomach out of its mouth and make it impossible for the fish to swim back to the depth from which it came.


What is “fizzing,” and does it really work to increase fish survival? 

Fizzing, or venting, is the procedure of puncturing a fish’s swim bladder with a sharp object, like a hypodermic needle, to release the excess gas and deflate it. While fizzing can relieve some symptoms of barotrauma, the few studies on this matter have shown that even if a fish swims away after it’s been fizzed, it may have lasting injuries that lead to death at a later time.


I’ve read that reeling in a fish really slowly can help. Is that true? 

In most cases, no. Some fish species, like salmon, pike or catfish, have a pneumatic duct that they can use to release, or “burp,” gases from their swim bladder. But walleye, perch and bass do not have this duct. They regulate gases in their swim bladder through their bloodstream, which takes quite a long time. So when most anglers consider reeling a fish in slowly (say 3-5 minutes) to allow them to release gas from their swim bladder, it’s not nearly slow enough to be effective.


What does the Department suggest an angler do when it comes to this issue? 

The Department strongly recommends that if you are fishing in waters deeper than 25-30 feet, you should make a conscience decision to keep everything that is caught, up to the daily limit, or spend your time fishing in shallower depths where barotrauma is not an issue.


How about the few lakes in North Dakota that have length minimums in place?

Most of the waters in North Dakota that have length limits do not have much for deep water to start with. In the few lakes that have deeper water and length restrictions, like  Jamestown and Pipestem reservoirs, anglers should simply avoid fishing the small areas of deep water unless they intend to keep the fish they catch.

Leier is an outreach biologist with the North Dakota Game & Fish Department.


Featured Photo:  Barotrauma is the term used to describe any of the number of injuries a fish may receive from rapid changes in atmospheric pressure while being reeled up.  Species like walleyes are more susceptible to the phenomenon. NDG&F Photo. 

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