Why should you vent or descend assist certain fish?

Reef fish taken from depths of 50 feet or more may undergo expansion of the gases in the swim bladder as they are brought quickly to the surface on hook and line. Swimbladders can expand only so far before they burst. Often the pressure is sufficient to push the stomach out of the mouth. It is a common misperception by anglers that this is the swim bladder, but it is the stomach. Venting involves using a sharp hollow instrument to puncture the body cavity wall and release the expanded gases so the fish can return to depth and have an increased chance of survival. 


An alternative to venting are descending devices, which bring fish back down to deeper waters, are another, more recently developed option that can now also be used to increase survival rates among fish with barotrauma. Maximizing post-release survival of fish is important in marine fisheries management because it means more fish survive to potentially reproduce and be harvested in the future.


While venting tools can still be a useful way to increase chances of survival after being released, fish do not always need to be vented.

Determining Which Fish to Vent

Scientific studies have shown that species with large swimbladders such as red grouper, black sea bass, and gag derive immediate benefit from venting. Your ability to judge which fish should be vented will improve with practice and experience. After reeling in a fish, closely observe its condition. If the fish is bloated and floats (is unable to control its buoyancy) or if the fish’s stomach is distended out of the mouth, the fish should be vented. If the fish appears normal, not bloated, and is able to swim down to habitat depth on its own, venting is not necessary.

Example of the stomach coming out of a snapper.

How to Vent a Fish

It is best to vent the fish as quickly as possible with a minimum of handling. If the fish’s stomach is everted out of the fish’s mouth, do not attempt to push it back into the fish’s body. Expelling the swimbladder gases will allow the stomach to return to its normal position within a few hours.


1.) Hold the fish gently but firmly on its side and insert the venting tool at a 45-degree angle approximately one to two inches back from the base of the pectoral fin. Only insert the tool deep enough to release the gases - do not skewer the fish. The sound of the escaping gas is audible and deflation is noticeable. If a fish is extremely bloated, use the hand holding the fish to exert gentle pressure on the fish’s abdomen to aid deflation.


2.) Keep a good grip on the venting tool during the entire process, so that an unexpected jerk from the fish does not dislodge the tool and cause injury to others. The fish’s everted stomach should not be punctured. This practice is not as efficient in releasing gas from the body cavity and results in additional injury.


3.) Return the fish to the water as soon as possible. If necessary, revive it by holding the fish with the head pointed downward and moving the fish back and forth to pass water over the gills until the fish is able to swim unassisted.

Descending Devices

The SeaQualizer is a pressure activated decompression tool designed as an alternative method to venting. It is recommended when fishing at depth that any fish returned should be released at between 1/3 to 1/2 the depth they were caught at. Once you choose your release depth attach the SeaQualizer to your fishes bottom lip and slowly send the fish back down. Once the SeaQualizer reaches set depth the jaws pop open allowing the fish to return itself to the bottom. This tool is completely non-invasive for the fish.
Modified dungenese crab trap.Works like the inverted utility crate. Anglers are constantly coming up with new devices.
RokLees Fish Descender. Developed in California. Fish is lowered and then released by a sharp tug on the line.

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