You let it go and it won’t go down.
It rights itself for a second, rolls onto its side, and drifts off on the current with its tail working and getting nowhere. Somebody on the boat says it’ll be fine once it gets its bearings. It might not be. A fish that can’t get back under after release is in real trouble from barotrauma, and that trouble started on the ride up, when the pressure changed.
In deepwater fish that are prone to it, barotrauma is a big reason released fish die anyway. Sending them back down with a descending device can improve their odds a lot, but it doesn’t guarantee anything. Survival still depends on the species, how deep it came from, what shape it’s in, and how it was handled and released.
What the ride up actually does to it.
Plenty of fish carry a swim bladder, a gas-filled organ that lets them hold depth without swimming. Down where the fish lives, that gas is balanced against the pressure around it. Reel a susceptible fish up quickly and the pressure falls away, so the gas expands faster than the fish can deal with.
None of it is mysterious. It’s pressure and plumbing. The expanding gas can push organs and tissue out of place and leave the fish floating like a cork, and a fish that can’t get back below the surface after release is stuck up there, stressed and easy for predators to find.
Stewardship · barotrauma
The gas expands on the way up, and it cannot get out fast enough
- swim bladder
- expanded past recovery
Source: NOAA Fisheries — Rockfish Barotrauma and Recompression.
What it looks like, and what it doesn’t.
The signs are pretty specific, and they’re worth knowing because half of them get mistaken for something else.
The stomach pushed out through the mouth. People misread this a lot, sometimes as a hook injury.
Bulging eyes, sometimes clouded. The pressure change inside the fish can do that.
A bloated, tight belly. In bad cases other tissue can push out as well.
And the one that matters most: it can’t get down. A fish that stays at the surface, or keeps floating back up, has lost control of its buoyancy.
Not every fish gets it. Sharks and rays don’t have a swim bladder at all. Species and depth matter most, along with how fast the fish came up and how it was handled. NOAA notes that barotrauma is common in reef fish brought up from about 90 feet or deeper, but it can happen in a lot shallower water than that.
Two tools, and they’re not equal anymore.
A descending device takes the fish back down and lets it go there. Most are a weighted clamp, an inverted hook or a lip-grip-style device on a heavy line that you lower to depth and then release. Nothing gets poked into the fish, but it still has to be clipped on right, carry enough weight, and go deep enough to actually recompress it.
A venting tool is a hollow tool used to let expanded gas out through the body wall. Where venting is allowed and you do it, the right tool, the right spot on the fish and the right technique all matter. A knife, an ice pick or anything else solid isn’t a venting tool.
For a lot of release situations, fisheries agencies are leaning more and more on recompression, partly because it takes the guesswork about where to put the needle out of the picture. Which method is right still depends on the fishery and the agency’s current guidance.
Either way, keep handling and air time short and get the fish back into suitable water fast.
Sources: NOAA Fisheries — California Recreational Rockfish Information · NOAA Fisheries — DESCEND Act device definitions · NOAA Fisheries — barotrauma depth note (90 feet, as shallow as 33 feet).
Straight, on the rules.
This went from good practice to law in some fisheries, but the exact requirement depends on where you’re fishing and when.
The DESCEND Act created a federal Gulf reef-fish requirement that vessels have a venting tool or descending device on board, rigged and ready for use. That federal requirement expired in January 2026. As of September 7, 2026, NOAA Fisheries is considering a proposed framework action that would continue it, but the continuation isn’t a final rule yet.
Other state and federal fisheries may have their own requirements or recommendations. Check the current rule for the exact water and species before you go, instead of assuming the old DESCEND Act requirement still applies.
Current-status source checked September 7, 2026: NOAA Fisheries — Continuation of Management Measures to Reduce Reef Fish Release Mortality.
The actual procedure, once.
Decide before the fish comes up whether it is likely to be released. If descending gear is appropriate for the fishery, have it rigged before it is needed.
Keep handling and air exposure short. Follow the device manufacturer’s instructions and the current fisheries-agency guidance for attachment point, weight, and release depth; descending devices differ in how they hold and release a fish. Lower the fish steadily to the recommended depth and release it there.
Depth matters to survival, but there is no single universal depth at which every fish needs recompression. NOAA’s California rockfish guidance, for example, estimates survival after descending at about 91% for similar demersal rockfish released from shallower than 180 feet, 70% from shallower than 300 feet, and 62% from shallower than 600 feet. Those are fishery-specific estimates, not a promise for every species.
Fishing wrecks and reefs → Deep drop → The saltwater system →
Correction — September 7, 2026. This page previously said the federal Gulf DESCEND Act gear requirement was still in force and described descending devices as a complete solution. The federal requirement expired in January 2026 and its proposed continuation is not yet final. The survival language has also been corrected to reflect species- and depth-dependent outcomes rather than guaranteed survival.