Greek word baros which means pressure. Trauma is the Greek word for “wound”. In our fishing in Alaska, the principle group of fish that barotrauma applies to are rockfish which have a gas filled swim bladder. This gases in the swim bladder are slowly extracted from the blood stream. The purpose of the swim bladder is to provide the fish with something close to neutral buoyancy at the depth they live, thus they don’t have to work hard to simply hang suspended in the water column.
The swim bladder of a rockfish living a couple hundred feet or more down in the water column is under immense pressure and may only be the size of your thumb when inflated for neutral buoyancy. When you bring that rockfish to the surface, the decrease in pressure results in an expansion of the air bladder so now it’s the size of a small party balloon. The air bladder pops out the mouth, bringing the stomach with it, the eyes bulge, the body appears bloated, and the fish has extreme positive buoyance, so much so that it cannot swim back down. If you simply let it go, it bobs around on the surface until it dies from injuries or from birds pecking away at it.
Many species of rockfish are very slow growing and old. They are easily overfished, but having limits makes no sense if all the fish you release end up dead. In the past few decades a great deal of research has been conducted on deep water releasing fish with barotrauma issues. It takes a heavy weight and a device that takes the fish down and releases it at the desired depth. If done properly, the release mortality goes from nearly 100% for effected fish released at the surface to something more like 20% or less according to some studies. That’s why we now have a law in Southeast Alaska requiring sport fishers to deep-water release all demersal shelf rockfish that aren’t retained.
There are a lot of devices made for this job. Here are just 4 of them:
- Fish Grip www.thefishgrip.net
- RokLees www.ecoleeser.com
- SeaQualizer www.theseaqualizer.com
- Shelton www.sheltonproducts.com
Capt. Tom’s favorite is the SeaQualizer (http://seaqualizer.com/) made in three sizes for release depths ranging from 30 to 300 feet. These clip on to the jaw of the fish and using a pressure sensitive mechanism release you rockfish at your designated setting. Everyone who encounters rockfish that they will have to release because of restrictions, should be prepared with a device that gets that fish back down where it will survive the experience.
There are some excellent videos that show a rockfish going back to depth. It’s an amazing transformation from the bloated, stomach/swim bladder sticking out, eyes bulging to looking like a normal fish as the depth increases. See below: