Every year, millions of Gulf of Mexico reef fish die after being caught and released.
There are several reasons why a fish may die after release – a term called discard mortality – but for reef fish, the biggest reason is barotrauma. Barotrauma refers to injuries sustained due to changes in pressure. Even at a depth of only 50 feet, the pressure is already more than twice that of the surface! As a result, when fish are caught from depths of 50 feet or greater, their swim bladders often expand like balloons and exert great force on the other internal organs.
Fish experiencing barotrauma typically have some combination of an inverted and protruding stomach, bulging eyes, distended intestines and/or a bloated belly. To make matters worse, fish experiencing it are generally unable to return to depth; if tossed overboard in their current state, they will likely float and struggle at the water’s surface.
After an extended period, these fish may eventually decompress enough to swim back down to depth; however, during this time, these fish are also very susceptible to death from predation, stress or barotrauma-related injuries.
Methods mitigate barotrauma
Fortunately, anglers can help mitigate the effects of barotrauma by using descending devices or venting tools. Descending devices work by returning a fish back to its original depth, thus allowing the fish’s swim bladder to naturally return to its original size. Venting tools are hypodermic needles used to pierce a fish’s swim bladder and allow gases to escape, thereby alleviating pressure and allowing the fish to swim downward.
These two methods have been proven to be so successful that, starting in 2022, all fishermen will be required to have a venting tool or descending device onboard when fishing for reef fish in the Gulf of Mexico. So, the question becomes, which method is better?
When used correctly, both descending devices and venting tools significantly improve post-release survival of fish experiencing barotrauma; however, each method has its advantages and disadvantages.
Descending devices return fish to depth
One advantage of using a descending device is that it is non-invasive, as it does not require any type of internal puncturing. Descending devices also return fish to their original capture depth; therefore, a fish that just spent a substantial amount of energy fighting on a hook doesn’t have to then exert additional energy swimming all the way back down.
Despite the benefits to the fish, when compared to venting, descending devices are more time-consuming to use and require a separate fishing rod to be rigged specifically for descending purposes. For that reason, this method may not be best in instances where fish are being caught faster than they can be descended.
Venting tools take less time
The biggest strength of venting tools is their speed. A properly trained angler can correctly vent and release a fish in a few seconds, whereas descending a fish takes much longer. Despite being quicker, venting a fish does cause some harm to the fish. While the puncture wound to the swim bladder heals quickly – generally within a day – it can take anywhere from days to weeks for the fish’s swim bladder to fully reacclimate, and the fish will not return to its original capture depth until this process is complete.
However, the biggest issue with venting tools by far is that a large portion of anglers vent fish incorrectly, and as a result, cause more harm than good. In fact, a 2013 study found that only about a quarter of surveyed anglers actually selected the correct location to vent a fish.
The problem with venting at “incorrect” locations is that in doing so, anglers are likely to not only pierce the fish’s swim bladder, but also its stomach, liver or other vital organs in the process. Unfortunately, this means that more than half of the surveyed anglers who use venting tools don’t actually improve the post-release survival of their fish, despite their best intentions.
Which should you use?
With all that said, which method should you use?
Well, the simple answer is to use descending devices when you can, and when you can’t, vent correctly. Most private recreational anglers should use descending devices because this method is the most beneficial to the fish. However, for deckhands on headboats where many people are fishing at once, venting is the right choice due to the frequency at which fish are likely to be caught. Either way, as long as you are using your chosen method correctly, you are significantly increasing the chance that your fish will survive after release.
If you want to learn more about the best release practices when fishing for offshore reef fish, then I highly recommend visiting https://returnemright.org/. There, you can watch instructional videos on how to properly use venting tools and different types of descending devices. You can also read summaries of scientific publications that have investigated the effectiveness of descending devices and venting tools. Finally, you can participate in educational modules focused on best fishing practices.