Barotrauma and Fish Descending Devices: What Every Angler Should Know

If you ever bottom-fish in deeper water, there’s a term you should know: barotrauma. It describes pressure-related injury that occurs when a fish is brought up too quickly from depth. Using a proper descending device to get the fish back to the bottom can dramatically improve its chances of survival — that’s good for the fishery and good for the angler. Let’s dive into what’s going on, how to spot the problem, what to do about it, and why it matters.

What is barotrauma?

Barotrauma is a kind of physical trauma that happens to fish when they’re brought rapidly from deep water to the surface. The culprit: the swim bladder (a gas-filled organ that helps fish control buoyancy) expands as the surrounding pressure drops. 

How and why it occurs

• As fish are pulled up from depth, water pressure decreases (roughly 1 atmosphere every ~33 ft) and the gas in the swim bladder expands.
• If the fish cannot release that gas (or its tissues cannot accommodate the expansion), organs may bulge, the fish becomes overly buoyant and/or unable to swim back down.
• The severity increases the deeper the fish is caught (and the faster the ascent) and depending on species, size, condition. 
• The expanded gas may force organs to distort (e.g., stomach everted out of mouth), eyes bulging, intestines distended, etc. 

Signs and symptoms of barotrauma

Knowing the signs helps you decide whether to deploy a descending device (or other method). Common signs:

• A stomach protruding from the fish’s mouth (might be mistaken for something else) 
• Bulging or crystallized eyes (“pop-eye”)
• Bloated mid-section, distended intestines, lifted or bubbly scales 
• Fish floating on surface, unable to swim downward, or struggling to descend.
• A firm body cavity (suggesting gas expansion) even if outward signs are subtle.

At what depths / species does it matter?

• Some fish begin to show signs at surprisingly shallow depths (33 ft) though many guidelines point to 50-65 ft or more.
• But deeper = more severe risk. For example, fish caught deeper than 180 ft that are released at the surface without a descending device have very high mortality.
• Species difference matters: bottom-fish and reef fish (rockfish, snapper, groupers etc.) that live deeper are more likely to suffer severe barotrauma.
  

What are descending devices — and how do they work?

Descending devices (aka recompression or release devices) are tools used to return fish suffering barotrauma back to depth, so that increased ambient pressure helps the fish’s swim bladder contract/return to normal and improves survival chances.
Here are some types:

• A jaw clamp / lip clamp device (for example the SeaQualizer). These may have pressure-activated release at depth.
• A weighted, inverted barbless hook or clamp (for example the SeaYaLater) that attaches to the fish and is lowered back to depth and then released.
  
• A weighted crate or net (milk crate style) that you drop the fish into (or under) and lower downward, letting the fish swim out once at depth.
• DIY vs commercial: Many anglers build simple versions; some buy branded devices. 
  The key is getting the fish back to a deeper pressure zone fast, minimizing time at surface, reducing stress, and allowing the fish to recover.

Descending devices vs venting tools

Another common question: should you vent (insert a needle to release gas) or descend?

• Venting tools: typically hollow needles or similar to puncture the swim bladder and release gas. Can be faster and require less rigging.
• But venting has risks: if done incorrectly it can injure the fish, introduce infection, reduce survival.
• Many recent guidelines emphasize that if you carry a device you’re more likely to get good survival by descending rather than venting. For instance: “Under most conditions, the descending device is the preferred method of release because it is the easiest to use and safest for the fish.” -Florida Sea Grant
• Regulations in some areas now require either a venting tool or a descending device, and in many cases recommend/require a descending device when signs of barotrauma are present.
  
  

How to use a descending device — step-by-step best practice

Be prepared: Before dropping a bait to the bottom, rig a dedicated descending-device rod or have a rope setup handy. Don’t wait until the fish is bleeding on deck. 

Recognize when use is needed: If the fish shows signs of barotrauma or if you caught fish in depth where barotrauma risk is high, plan to use the device. Even if signs are not obvious but depth was large, many experts err on the side of descending.

Attach the device:

• • Lip clamp: clamp the device to the fish’s lower jaw/hook area.
  • Inverted hook: hook through lower jaw (or as specified).
  • Weigh the line/rope appropriately.
  • Or, put the fish into a weighted crate/net.

Lower the fish back to depth: Use a weight heavy enough to reach the depth from which the fish came. 

• • A rule-of-thumb: 1 lb of weight for every 5 lb of fish has been suggested for some devices.
  • Use a designated rod or rope so the drop is quick and controlled. Avoid drag, snags, long delays.

Release the fish at depth: Once at the desired depth the pressure will trigger the device, and release the fish. Monitor that it swims off strongly.

Minimize handling time and surface exposure: The less time the fish spends at the surface (and out of the water), the better its survival odds.

Record/observe: If you’re collecting data, note species, depth, signs, outcome. Helps build best-practice.

Avoid venting unless trained: Unless you’re very confident in proper venting technique, descending is generally safer. If you do vent, follow precise instructions and only when necessary.

Regulations & fishery conservation implications

• Several states and federal agencies now require that when fishing for certain reef or bottom dwelling species, a descending device (or venting tool) must be carried and ready. E.g., in California: “A descending device must be carried aboard and available for immediate use on any vessel taking or possessing any species of federal bottom dwelling.”
• Failure to comply can lead to regulatory risk and fisheries closures.
• From a conservation angle: returning fish with barotrauma properly means lower mortality, healthier stocks, longer seasons, and more sustainable fishing.