Releasing Fish Caught in Deep Water

Black sea bass and other reef fish are often caught in water deep enough to hurt them on the way up. Release one at the surface and it may float there, belly up and unable to swim down, until a gull finds it. That's barotrauma. If you fish deep structure and release fish, and with size limits you'll release plenty, learning to send them back down properly is part of the job.

What's happening

Fish like sea bass have a gas-filled swim bladder that keeps them neutrally buoyant at the depth they live. Water pressure goes up about one atmosphere for every 33 feet of depth. When you reel a fish up fast, the pressure drops and the gas in its swim bladder expands, like a balloon rising. The expanding gas pushes on the fish's organs and can leave it too buoyant to swim back down.

Fish caught in water deeper than about 30 feet often show some effects, and barotrauma gets worse the deeper you go. In sea bass, signs can show up from as shallow as about 65 feet. In one deep winter sea bass fishery off New Jersey, in 150 to 220 feet of water, nearly all the fish showed signs, and up to about half died after being released at the surface.

The signs

• Bulging eyes
• A swollen, tight belly
• The stomach pushed out of the mouth (it looks like a pink balloon)
• Intestines pushed out of the vent
• The fish floats or swims weakly at the surface and can't get down

That balloon in the mouth is the stomach, not the swim bladder. Never pop it or cut it.

Send it back down: descending devices

The best way to save a fish with barotrauma is to return it quickly to the depth it came from, where the pressure squeezes the gas back down. Research shows descending devices are the most effective way to do it. There are a few kinds:

• Lip clamps: a weighted clip that holds the fish by the lip.
• Inverted hooks: a weighted hook pointed up that holds the fish by the lip.
• Weighted baskets or hoop nets ("fish elevators"): the fish goes in and rides the device back down.

How to use one:

1. Have it rigged and ready before you start catching fish, on a heavy rod or a handline. Some areas require one on board.
2. Use enough weight, roughly a pound for every 5 pounds of fish, to pull the fish down against its buoyancy.
3. Attach the fish quickly and lower it, ideally close to the bottom it came from, or at least deep enough that it can swim on its own.
4. Release it and bring the device back up.

Venting: only if you can't descend

Venting means letting gas out of the swim bladder with a hollow needle so the fish can swim down. It works, and studies on sea bass have shown proper venting raises survival compared with doing nothing. But it's easy to do wrong, it can injure the fish or cause infection, and many agencies now recommend descending devices first.

If you must vent:

• Use only a proper venting tool: a hollow, sharp needle. Never a knife, ice pick or hook.
• Insert it behind the pectoral fin at about a 45-degree angle, just deep enough to release the gas.
• Never pierce the stomach sticking out of the mouth.

Handle fish well at the surface

Barotrauma isn't the only thing that kills released fish. A long fight and rough handling lower survival too.

• Use circle hooks on bait rigs. They hook fish in the jaw and make quick release easy.
• Use a dehooker. With a circle hook, you can often flip a small fish off the hook and back into the water without touching it.
• Don't keep fishing a spot full of shorts. If most of your fish are too small, move to deeper or different structure where the bigger ones are. See Black Sea Bass: Where They Live Through the Year.

Fish you release properly today are the keepers someone catches next season. For rigs that make release easier, see Black Sea Bass Rigs and Jigs.