Barotrauma Basics

The arrow is pointing to an
inflated swim bladder

Many marine reef fish have a unique organ called a swimbladder. The gas-filled sac, which is attached to a fish's backbone beneath the dorsal fin, helps control buoyancy and allows the fish to maintain various depths in the water column. When a fish is brought up from depth during fishing, the decreasing pressure can cause the gases (mostly oxygen, nitrogen, and carbon dioxide) inside it's swimbladder to expand and rupture the organ. The escaped gases will continue to expand into the fish's body cavity, and the pressure exerted by them is sufficient to push the stomach out the mouth and the intestines out of the anus. Other symptoms may include a swollen belly or buldging eyes.




A grouper showing the signs of
barotrauma

This process, known as barotrauma, can result in serious injury to the fish and prevent if from returning back down to depth on its own if left in this state. Fish released in this condition may float away and die from exposure to the elements or become an easy target for predators.
Dealing with barotrauma has become as major challenge to fisheries managers. Allowing fish to simply float off after being released defeats the purpose of having regulations for minimum size restrictions and bag limits.
Several tools have been developed by researchers and fishermen to help address the issue of barotrauma.Venting involves inserting a hollow, sharpened needle into the side of a fish to release trapped gases so the fish is able to quickly return to a safe depth. Recompression involves returning a bloated fish to a safe depth with the aid of a cage, basket, or weighted hook or lip device.
Neither method is full proof or applicable in all conditions (or for all fish), but research studies have shown that when used in the right conditions venting and recompression can play an important role in  reducing mortality rates associated with fish suffering from barotrauma.
Stay tuned to learn more about these efforts as there are several initiatives at the local, state, regional, and national level to investigate the continued use of the conservation tools. In the meantime if you'd like to learn more about venting and recompression visit: catchandrelease.org

venting a red grouper

Returning a red grouper with a recompression device