Barotrauma: Understanding the signs of fish distress can mean everything
The causes and effects of barotrauma, how to prevent it and what tools anglers should have to assist distressed fish
DICKINSON — With summer heating up, many a North Dakota angler will head to the many lakes and rivers in search of that exhilarating catch and release of a hefty bass or sparkling, yellow perch.
North Dakota Game and Fish caution anglers to consider their role as conservationist by remaining vigilant and exercising caution for signs of barotrauma.
Barotrauma is a common injury, or barometric pressure trauma, that may occur to a fish as a result of rapid changes in pressures as they are reeled to the surface from water that is 33 feet deep or deeper. Barotrauma injuries may include hemorrhaging of internal organs, loss of vision, torsion of the stomach and more. Ultimately, unrecognized barotrauma can lead to immediate or delayed death.
Bulging eyes, bleeding gills, bubbly skin or an expanded swim bladder protruding from the fish’s mouth are symptoms of barotrauma and failure to identify them means a slow and painful death after the fish swims away.
“With swim bladder damage, the fish can’t keep themselves in equilibrium in the water so there is a fair amount of delayed mortality that anglers don’t see,” said Greg Power, North Dakota Game and Fish fisheries division chief.
Not all fish respond the same way to barotrauma, Power explained. Some species, such as largemouth bass, smallmouth bass, white bass, walleye and yellow perch, are more susceptible to barotrauma because they do not have a duct connecting their swim bladder to their stomach. Instead, these fish regulate their swim bladder by releasing gasses through their gills via the bloodstream.
Trout, salmon and pike are not as at risk for barotrauma because they do have the useful duct that connects their swim bladder to their stomach, allowing them to expel air to decompress their swim bladder as they are reeled from deep water.
Barotrauma is not prominent everywhere in North Dakota, because most lakes in the area don’t exceed 33 feet in depth. Fish in Lake Sakakawea and Devils Lake are more likely to experience barotrauma because these bodies of water are larger and deeper.
To reduce the risk of this fish fiasco, anglers should avoid catch and release fishing for bass, walleye or yellow perch in areas of deep water. Those who do fish in deep water should intend to harvest all legal fish they catch. Anglers who do practice catch and release fishing should do so in shallow water to increase the likelihood of survival of the fish they release. Puncturing the fish’s swim bladder, also known as venting, has been used by anglers to help the fish swim to its original depth, but this is not a safe option for the fish, Power said.
“Fizzing (venting) and descending tools all sound great…but the reality is that there are thousands of anglers out there,” Power said. “A couple may be able to get that process down and do a good job with it, but it certainly isn’t the right answer. Most people will not take the time to do it right and we strongly recommend against it.”
Descending devices is a tool that can be used by anglers to return fish to depths where increased pressure from the water will assist in recompressing their swim bladder gases. These devices come in three categories, including mouth clamps, inverted hooks and fish elevators.
To learn more about descending devices and how to use them, anglers can watch “How-to Videos” on YouTube by searching for “Barotrauma.”
Venting tools are sharpened, hollow instruments that anglers can use to treat barotrauma by releasing expanded gas from the swim bladder, enabling the fish to swim back down to capture depth.
Please note, items such as fillet knives, ice picks, screwdrivers and gaffs are not venting tools and should never be used to vent a fish. Venting a fish incorrectly, or with the wrong tool, may cause more harm than good.
To properly vent, lay the fish on its side (on a cool, wet surface). Insert the venting tool at a 45-degree angle, under a scale 1-2 inches behind the base of the pectoral fin, just deep enough to release trapped gasses. Never insert venting tools into a fish’s belly, back or stomach that may be protruding from the mouth.
The North Dakota Game and Fish Department advises exercising caution and understanding the effects of barotrauma to minimize this problem and to extend the long-term health of fish.
"When fishing deep, keep the catch," Power said. "Don’t release the fish in 30 plus feet of water."
For additional information about barotrauma visit https://gf.nd.gov/fishing/barotrauma .