Barotrauma Also is Deadly in Freshwater Fish

North Dakota issues a warning to anglers hauling summer deep-water fish up from the depths that they may suffer the bends, just as marine fish often do when raised from deep ocean water.
Barotrauma in a fish
Barotrauma is deadly to both fresh and saltwater fish. Courtesy North Dakota Game and Fish Department

Saltwater anglers often have to deal with releasing marine fish suffering from “the bends”, or more properly known as barotrauma. But freshwater fish hauled from the dark reaches of lakes can suffer the same barotrauma fate, and it can be fatal to fish that are released, reports the North Dakota’s Game and Fish Department (NDGFD).

“When the bite first started, anglers were catching fish in shallow water,” says NDGFD Missouri River System Supervisor Dave Fryda. “As the summer progressed, fish move into deeper water and are now being caught at depths where barotrauma is a concern.”

So North Dakota fisheries personnel are encouraging anglers to keep fish caught from depths of more than 25 feet, rather than practice catch-and-release of fish that may have baratrauma.

Barotrauma occurs when a change in water pressure causes a fish’s swim bladder to expand, which means the fish can no longer control balance. In addition, reports the DNGFD, other internal injuries are likely, such as ruptured blood vessels or damaged internal organs.

Because of these potential internal injuries, NDGFD biologists discourage fizzing, the practice of deflating a fish’s swim bladder. Instead, when freshwater walleyes, pike, lake trout or other deep species display signs of barotrauma, North Dakota officials believe keeping such fish is better than releasing them, in case they die afterward and are wasted.

Barotrauma injury can happen in any deep-water body, but it is especially noteworthy during summer in Lake Sakakawea, ND.

Prior to fishing at least 25 feet deep, anglers should make a decision to keep what they catch prior to fishing and honor that commitment, say NDGFD officials.

In saltwater, however, anglers working for deep water fish such as amberjack, snapper, grouper, and others that have “the bends” have been long-schooled and advised to “fizz” fish, or take them back deep with several specially-designed devices for this purpose.

In some states, having such devices on board is mandatory for marine fishing. This is so that snapper, grouper and other species caught can be released with survival more likely than just tossing them overboard and hoping they live another day.

In many states with strict size limits and closed season on marine bottomfish, releasing some deep species is required. It’s not an option to keep them for home use if they have barotrauma.

Several methods of getting fish back down to their preferred depths work well, according to the Florida Fish and Wildlife Conservation Commission (FWC). They have a very detailed YouTube video that shows how to use various devices and techniques to release deep fish that may have “the bends.”

“Descending devices” are one type of tool, consisting of weights that attach to a fish and help take it back to an appropriate depth. There are various types of descending devices but the most common are “lip clamps,” “inverted hooks” and “fish elevators.”

“Fish elevators” are one of the simplest and most effective descending devices. Milk crates are great for this, but they have limitations because of their relatively small fish holding capacity. Plus they are bulky inside a boat full of fishermen and other gear.

Venting tools also can be used to puncture a fish’s swim bladder, allowing expanding gas to escape so a fish can swim back to the bottom.

Proper venting tools are sharp and pointed instruments. Fillet knives, ice picks, scissors, screwdrivers and hook points should not be used to vent fish, since they can cause more harm than good.

Venting must be done properly, and the FWC video footage is helpful in learning how to do it.

A proper venting tool should be inserted two to three inches behind the base of a fish’s pectoral fin. Inserted under a scale at a 45-degree angle, and inserting into a fish just deep enough to release gas from the swim bladder usually does the job.