Releasing Fish Caught from Deep Water
Fish that are caught in deep water and released may face additional challenges to survival. Some marine fish, such as snappers and groupers, have a gas-filled organ called a swim bladder that controls buoyancy and allows the fish to maintain a certain depth. When fish are pulled up from deep water (typically depths greater than 50 feet), the change in pressure can cause the gas in the swim bladder to expand and in some cases burst. Damage to the swim bladder or other internal organs that is caused by such change in pressure is called barotrauma.
When a fish suffering from barotrauma is released, it is unable to swim back down to capture depth making it difficult to survive the elements and avoid predators. If a fish needs to be released and shows any or all of these signs of barotrauma, venting tools and descending devices may increase the fish’s chance of survival after release.
If the stomach is protruding from the mouth of the fish, do not puncture or push the stomach back in. When the fish swims back down to depth it will re-ingest its stomach. Return the fish to the water as soon as possible and, if necessary, revive the fish by moving the fish forward in the water allowing water to pass over the gills.
Watch this video to learn how to treat barotrauma. Read about our 2017 FWC Citizen Science Descending Device Study Final Report - An Evaluation of Anglers' Barriers to Using Descending Devices.
Venting tools are sharpened, hollow instruments such as a hypodermic syringe with the plunger removed or a 16-gauge needle fixed to a hollow wooden dowel. These devices are used to treat barotrauma by releasing expanded gas from the fish body cavity, enabling fish to swim back to capture depth after release. A variety of venting tools are available in bait and tackle stores. Knives or an ice-pick are not venting tools because they do not allow the expanded gases to escape from inside the body.
How to vent
Vent the fish as quickly as you can. Gently hold the fish on its side and insert the needle into the body cavity at a 45-degree angle under a scale. The area to insert the venting tool is approximately 1 to 2 inches behind the base of the pectoral fin. Insert the venting tool just deep enough to release the expanded gases. You may hear an audible release of this gas.
Venting helps release gases that may over-expand in the body cavity when fish are brought to the surface from deep water. Remember to only use a venting tool or descending device when one or all of the signs of barotrauma are present. Watch this video to learn how to vent a fish properly.
A descending device (recompression device) is a tool that is used to reverse the effects of barotrauma. The device descends fish back down to a depth where the increased pressure from the water will recompress the swim bladder gases and allow the fish to swim away. In recent years, a number of descending devices have been developed. The type of descending device to use is often based on individual angler preference.
Most devices are weighted and attached to fishing line (or rope) and clamp or hook on to the mouth of the fish. The angler lowers the device and fish back down to a depth where the fish can recover from barotrauma and then releases the fish. Another option is a fish elevator, a bottomless cage which allows the gases to recompress while the fish is brought down to capture depth.
Although more research is being conducted, there are indications that use of descending devices can increase survival of released fish. If you choose to use a descending device, follow the instructions on the package carefully to ensure the device is used properly. Watch our descending devices playlist to learn more.
Read about our 2017 FWC Citizen Science Descending Device Study Final Report - An Evaluation of Anglers' Barriers to Using Descending Devices.
Where to Get a Descending Device
Some descending devices are available in retail shops, or you can even make your own device. If you are unable to locate the device you want from a local store, you can also find various models for sale online or by clicking the following links: SeaQualizer, RokLees, Fish Saver, Shelton Fish Descender, Safe Release Weight, SeeYaLater Fish Release Hook
These links are provided to help anglers find a descending device and do not constitute an endorsement of any product.
Mouth clamps are attached to a rod and reel and use a pressure sensor (releases fish automatically at a predetermined depth selected by the angler) or a weighted spring release mechanism (lets go of fish after the angler gives a sharp tug on the line).
Learn how to use SeaQualizer and RokLees descending devices.
Inverted hooks work similar to mouth clamp devices, but are inserted through the hole made by the hook. Once the fish is deep enough to reverse the effects of barotrauma, the angler reels up the line and the fish swims away. This method is fairly inexpensive, but takes practice.
Learn how to use Fish Saver and Shelton Fish Descender devices. Learn how to make your own inverted hook descending device.
A fish elevator, such as an inverted milk crate with a rope attached to the top and weights at each corner, creates a bottomless cage which allows the gases to recompress while the fish is brought down to capture depth. Ensure the inside of your fish elevator/crate is smooth to help reduce the chance of removing the fish’s protective slime layer.
Learn how to use a milk crate descending device.
Signs of Barotrauma
How to Treat Barotrauma
Learn about the tools available to treat barotrauma, a condition that occurs when fish are brought up from deep waters. Knowing how to and using venting tools and descending devices can help fish survive after being released.Watch Video
Fish Handling & Gear
There are lots of things you can do to give the fish you release a fighting chance!